What are Modal Verbs? Definition and Examples

Modal verbs are a powerful tool in the English language used to assert expressions in a sentence, like polite requests and strong obligations. While they might come across as complicated in the beginning, mastering them will help you communicate clearly and more precisely. Let's explore how they work and how to use them effectively.

Key Takeaways:

• Modal verbs are auxiliary verbs that express possibility, ability, permission, necessity, and obligation, including words like can, should, must, and will.

• The most common modal verbs are can, could, may, might, will, would, shall, should, must, and ought to.

• Modal verbs are followed by the base form of the main verb (infinitive without "to") and don't change form based on the subject.

• They help us express attitudes toward actions rather than stating facts directly.

• Understanding modal verbs is essential for expressing nuance, politeness, and different levels of certainty in English.

What are Modal Verbs?

Modal verbs, also called auxiliary verbs, are special helping verbs that help us to assess the speaker’s attitude towards a situation or correspondence. Unlike regular verbs that describe actions or states, modal verbs indicate possibility, ability, permission, obligation, or necessity.

Modal verbs function as auxiliaries, meaning they work alongside main verbs to add meaning. They never appear alone as the main verb in a sentence (except in short answers).

Consider these two sentences:

• I drive to work. 

• I can drive to work.

The first sentence shares a fact, while the second uses the modal verb "can" to talk about ability or possibility. This small change makes a significant difference; it transforms a simple statement into an expression of capability, adding depth to its meaning.

Key Characteristics of Modal Verbs

Modal verbs have several unique grammatical features:

• They don't change form. Unlike regular verbs, modal verbs stay the same regardless of the subject. You say "he can swim," not "he cans swim."

• They're followed by the base form. The main verb that follows a modal verb appears in its infinitive form without "to." For example: "She might leave" (not "She might to leave").

• They create questions by inverting. To form questions, simply move the modal verb before the subject: "Can you help me?"

• They form negatives easily. Add "not" after the modal verb to make it negative: "You should not worry" or the contracted form "You shouldn't worry."

List of Modal Verbs

Let’s discuss all the modal verbs and their respective examples.

Core Modal Verbs

The main modal verbs you'll use most frequently are:

• Can – ability, possibility, permission

• Could – past ability, polite requests, possibility

• May – permission, possibility

• Might – possibility (less certain than may)

• Will – future intentions, predictions, willingness

• Would – polite requests, hypothetical situations, past habits

• Shall – formal future, suggestions (primarily British English)

• Should – advice, recommendations, expectations

• Must – strong necessity, obligation, logical conclusion

• Ought to – moral obligation, advice

Semi-Modal Verbs

These expressions function similarly to modal verbs but have slightly different grammatical properties:

• Have to – necessity, obligation

• Need to – necessity

• Be able to – ability (alternative to "can")

• Be going to – future plans, predictions

• Used to – past habits or states

When to Use Modal Verbs?

Modal verbs serve many purposes in English. Here are the main uses with clear examples:

Ability

Use "can" and "could" to express ability or capability.

Present ability:

• I can speak three languages fluently.

• She can solve complex math problems quickly.

Past ability:

• When I was younger, I could run five miles without stopping.

• He could play the piano beautifully before his injury.

Note: For ability in other tenses, use "be able to" instead: "I will be able to attend the meeting tomorrow."

Possibility

Express possibility using "can," "could," "may," or "might."

Present or future possibility:

• The package may arrive today.

• It might rain this afternoon.

• This could be the solution we've been looking for.

Past possibility:

• She might have missed the train.

• They could have taken a different route.

The choice between these modals indicates different levels of certainty, with "might" suggesting less certainty than "may."

Permission

Ask for or grant permission using "can," "could," "may," or "might."

Asking permission:

• Can I borrow your pen?

• Could I leave early today?

• May I speak with you privately?

Granting permission:

• You may use my office while I'm away.

• Students can submit assignments by email.

"May" is traditionally considered more formal and polite, though "can" is widely accepted in modern usage.

Requests

Make requests using "can," "could," "will," or "would."

Direct requests:

• Can you close the window?

• Will you help me with this project?

Polite requests:

• Could you please send me the report?

• Would you mind calling me back later?

"Could" and "would" are generally more polite than "can" and "will," making them better choices in formal situations.

Advice and Suggestions

Use "should" and "ought to" for advice and recommendations.

Giving advice:

• You should see a doctor about that cough.

• We ought to leave earlier to avoid traffic.

• You shouldn't skip breakfast before an exam.

Making suggestions:

• We should try that new restaurant downtown.

• You ought to read this book—it's excellent.

Obligation and Necessity

Express obligation using "must," "have to," or "need to."

Strong obligation:

• You must wear a seatbelt while driving.

• All employees must attend the safety training.

General necessity:

• I have to finish this report by Friday.

• We need to buy groceries this weekend.

Lack of necessity:

• You don't have to bring anything to the party.

• She doesn't need to arrive early.

Prohibition:

• You must not share confidential information.

• Students mustn't use phones during exams.

Logical Deduction

Use "must" and "can't" to express logical conclusions.

Certainty:

• She must be tired after working all night. (I'm certain she's tired)

• They must have forgotten about the meeting. (That's the only logical explanation)

Impossibility:

• That can't be right. Check your calculations.

• He can't have left already; his coat is still here.

Probability and Expectation

Express likelihood using "should" or "ought to."

Expected outcomes:

• The train should arrive at 3:00 PM.

• This ought to be enough food for everyone.

• The package should have arrived by now.

Willingness and Promises

Use "will" to express willingness or make promises.

Willingness:

• I'll help you move this weekend.

• Don't worry, I'll take care of it.

Promises:

• I will never forget your kindness.

• We'll deliver your order within two business days.

Past Habits

Use "would" or "used to" to describe past habits.

Repeated past actions:

• Every summer, we would visit my grandparents in the countryside.

• She would always arrive exactly on time.

Past states:

• I used to live in Boston before moving to Seattle.

• This building used to be a factory.

Note: "Used to" works for both habits and states, while "would" typically only describes repeated actions.

How to Use Modal Verbs

Let’s understand the right ways through which we can use modal verbs.

Basic Sentence Structure

Modal verbs follow a simple pattern in affirmative sentences:

Formula: Subject + Modal Verb + Base Form of Main Verb

Examples:

• I can swim.

• She should study harder.

• They must arrive on time.

• We will attend the conference.

Forming Questions

To create questions with modal verbs, invert the subject and the modal verb:

Formula: Modal Verb + Subject + Base Form of Main Verb

Examples:

• Can you swim?

• Should she study harder?

• Must they arrive on time?

• Will we attend the conference?

Forming Negatives

Add "not" after the modal verb to create negative sentences:

Formula: Subject + Modal Verb + Not + Base Form of Main Verb

Examples:

• I cannot swim. (or: I can't swim)

• She should not worry. (or: She shouldn't worry)

• They must not be late. (or: They mustn't be late)

• We will not attend. (or: We won't attend)

Common Contractions

Modal verbs frequently appear in contracted forms, especially in spoken English:

• can't (cannot)

• couldn't (could not)

• won't (will not)

• wouldn't (would not)

• shouldn't (should not)

• mustn't (must not)

• mightn't (might not) – less common

• shan't (shall not) – primarily British English

Note: "May" does not have a standard contraction.

Modal Verbs in Different Tenses

Present Tense

For simple present actions, use the modal verb with the base form:

• I can speak Spanish.

• She must leave now.

• They should arrive soon.

Present Continuous

To express ongoing actions, use: Modal + be + verb-ing

Examples:

• She must be working late tonight.

• They might be waiting for us at the restaurant.

• He should be arriving any minute now.

Present Perfect

For actions connecting the past to present, use: Modal + have + past participle

Examples:

• You should have called me yesterday.

• She might have forgotten about the appointment.

• They must have taken the wrong route.

Present Perfect Continuous

For ongoing actions from past to present, use: Modal + have been + verb-ing

Examples:

• He must have been working all night—he looks exhausted.

• They might have been waiting for hours.

• She should have been studying instead of watching TV.

Past Tense

Only a few modal verbs have distinct past forms: "could" (past of "can") and "would" (past of "will"). For other past meanings, use the present perfect structure.

Simple past:

• I could swim when I was five years old.

• Every day, he would walk to school. (past habit)

Past with present perfect:

• She may have missed her flight.

• You should have been more careful.

Future Tense

For future actions, "will" is already a modal verb. For other modals, they naturally refer to future time when context makes it clear:

Examples:

• I will call you tomorrow. (using "will")

• She might visit next week. (future possibility)

• We should finish by Friday. (future expectation)

• You can start the project on Monday. (future ability/permission)

Common Mistakes to Avoid

Let’s look at some of the mistakes people make while they are using modal verbs in their communication.

Adding ‘to’ After Modal Verbs

• Incorrect: She can to speak French. 

• Correct: She can speak French.

• Exception: "Ought to," "have to," and "need to" do include "to."

Changing Modal Verbs for Different Subjects

• Incorrect: He cans swim very well. 

• Correct: He can swim very well.

• Modal verbs never add -s, -ed, or -ing endings.

Using Two Modal Verbs Together

• Incorrect: She will can come tomorrow. 

• Correct: She will be able to come tomorrow.

• You cannot use two modal verbs consecutively. Use alternative expressions instead.

Confusing "Must" and "Have To"

While similar, ‘must’ often expresses the speaker’s opinion about necessity, while ‘have to’ refers to external obligations. 

• I must exercise more. (my decision)

• I have to attend the meeting. (required by my job)

Using "Must" for Negative Deduction

• Incorrect: He must not be at home. (This means prohibition) 

• Correct: He can't be at home. (This means logical impossibility)

• For negative deductions, use "can't" or "couldn't," not "must not."

Forgetting the Past Perfect Form

• Incorrect: You should call me yesterday. 

• Correct: You should have called me yesterday.

• For past reference with advice, regret, or criticism, use "modal + have + past participle."

Conclusion

Modal verbs are as important as main verbs; they are responsible for giving more clarity to the communication. Therefore, a good command of modal verbs will help you become a better writer and help you comprehend the language in a better way.

FAQs (Frequently-Asked Questions)

Q1. What's the difference between "can" and "may"?

Ans. Both express permission and possibility, but "may" is more formal. "Can" emphasizes ability alongside permission, while "may" focuses purely on permission. In modern usage, both are acceptable for asking permission, though "may" remains more polite in formal contexts.

Q2. When should I use "must" versus "have to"?

Ans. "Must" typically expresses the speaker's strong opinion or internal obligation, while "have to" indicates external necessity or rules imposed by others. However, in questions, use "have to" instead of "must": "Do I have to attend?" not "Must I attend?"

Q3. Can I use modal verbs in the past tense?

Ans. Only "could" and "would" function as direct past tense forms. For other past meanings, combine modal verbs with "have + past participle": "She might have left already." For past ability in affirmative sentences, use "was/were able to" rather than "could."

Q4. What's the difference between "should" and "ought to"?

Ans. These are nearly identical, both expressing advice or expectation. "Should" is far more common in modern English, while "ought to" sounds slightly more formal or old-fashioned. "Should" is also easier to use in questions and negatives.

Q5. How do I make modal verbs more polite?

Ans. Use "could" instead of "can," "would" instead of "will," and "might" instead of "may." Adding "please," "possibly," or "perhaps" also increases politeness: "Could you possibly help me with this?"

Q6. Can modal verbs be used in continuous tenses?

Ans. Modal verbs themselves don't have continuous forms, but they can be followed by continuous verb forms: "She must be working" or "They might be sleeping." This structure indicates ongoing actions.

Q7. What does "would" mean in the past tense?

Ans. "Would" describes past habits or repeated actions: "Every Sunday, we would visit the park." It's similar to "used to" but typically doesn't describe past states. You can say "I used to live there," but not "I would live there."

Q8. Why can't I say "I can to swim"?

Ans. Modal verbs are followed by the base form of the verb (the infinitive without "to"). The structure is: modal + base verb. So it's "I can swim," not "I can to swim." The exceptions are "ought to," "have to," and "need to," which include "to."

Q9. How certain is "might" compared to other modals?

Ans. "Might" expresses a low possibility (perhaps a 20-40% chance). "May" is slightly more certain (40-50%). "Could" is similar to "might," but it sometimes suggests a greater possibility. "Will" expresses certainty about the future, while "should" suggests strong expectation (70-80% certainty).

Q10. Can I use double modals in English?

Ans. Standard English doesn't allow two modal verbs to be used together. Instead of "I will can go," use alternative expressions: "I will be able to go." However, some regional dialects (particularly in Southern American English) do use double modals in casual speech.