Modal verbs are small helping verbs that add meaning to the main verb. They show ability, possibility, permission, advice, obligation and more. Compare I swim with I can swim, I should swim and I must swim. Each modal changes the meaning.
The main modal verbs in English are can, could, may, might, must, shall, should, will, would and ought to. Some grammar books also include semi-modals like have to, need to and be able to.
This guide explains each modal verb with simple rules and examples.
Basic Rules of Modal Verbs
- Modal + base verb: She can sing, not She can sings or She can to sing.
- No -s for he/she/it: He must go, not He musts go.
- Negative with not: cannot (can’t), should not (shouldn’t), must not (mustn’t).
- Questions by inversion: Can you help me? Should I wait?
- No past or future forms for most modals. Use other words: could or was able to for past ability; will be able to for future ability.
The British Council gives a clear overview in its modal verbs grammar reference.
Can
- Ability: I can speak three languages.
- Permission (informal): Can I use your pen?
- Request: Can you close the door, please?
- Possibility: It can get very hot in May.
Negative: She cannot (can’t) drive.
Could
- Past ability: I could read when I was four.
- Polite request: Could you help me with this bag?
- Possibility: It could rain later.
- Suggestion: We could go to the park.
Could is more polite than can in requests.
May
- Formal permission: May I come in, sir?
- Possibility: He may be late today.
- Wishes: May you live long!
Might
- Weaker possibility: I might visit my cousins this weekend, but I’m not sure.
- Past of may in reported speech: She said she might come.
May and might are often similar, but might usually sounds less certain.
Must
- Strong obligation (often from the speaker): I must finish this today.
- Rules and laws: Passengers must wear seat belts.
- Strong certainty: You must be tired after the journey.
Must not (mustn’t) means it is not allowed: You mustn’t use phones in the exam hall.
Have to
Have to is not a true modal, but it is used for obligation, often from outside rules.
- I have to wear a uniform at school.
- She has to work on Saturdays.
Important difference: don’t have to means it is not necessary, while mustn’t means it is not allowed.
- You don’t have to come. (You can if you want.)
- You mustn’t come. (It is forbidden.)
The British Council explains these differences in its page on suggestions and obligations.
Should and Ought to
- Advice: You should see a doctor. / You ought to see a doctor.
- Expectation: The bus should arrive soon.
- Duty: We should respect our elders.
Should and ought to have almost the same meaning. Should is more common in everyday speech.
Shall
- Offers and suggestions (with I/we): Shall I open the window? Shall we go?
- Formal future (older or legal English): The meeting shall begin at 10 a.m.
Will
- Future: I will call you tomorrow.
- Promises: I will help you, I promise.
- Instant decisions: The phone is ringing. I’ll answer it.
- Requests: Will you pass the salt?
Would
- Polite requests and offers: Would you like some tea?
- Imaginary situations: If I had wings, I would fly.
- Past habits: When I was young, we would play cricket every evening.
- Preferences: I would rather walk.
Modal Verbs Summary Table
| Meaning | Modal verbs | Example |
|---|---|---|
| Ability | can, could, be able to | She can swim. |
| Permission | can, could, may | May I leave early? |
| Request | can, could, will, would | Could you help me? |
| Possibility | may, might, could | It might snow. |
| Advice | should, ought to | You should rest. |
| Obligation | must, have to | I must study. |
| Prohibition | mustn’t, can’t | You mustn’t smoke here. |
| No necessity | don’t have to, needn’t | You needn’t hurry. |
| Offer / suggestion | shall, can, could | Shall I carry it? |
Modals in the Past (Modal + have + past participle)
- Should have: regret or criticism. I should have studied more.
- Could have: a past possibility that did not happen. We could have won.
- Must have: a strong guess about the past. She must have forgotten.
- Might have: a weak guess about the past. He might have missed the bus.
Common Mistakes
| Wrong | Right |
|---|---|
| He can speaks English. | He can speak English. |
| You must to go. | You must go. |
| She shoulds study. | She should study. |
| I will can come. | I will be able to come. |
| You mustn’t come tomorrow. (meaning not necessary) | You don’t have to come tomorrow. |
The Cambridge Dictionary blog has a friendly post on modal verbs: the basics if you want another explanation.
Practice: Choose the Right Modal
- You ___ wear a helmet when riding a motorbike. (must / might)
- ___ I borrow your book? (May / Must)
- She ___ play the piano when she was six. (could / can)
- You look ill. You ___ see a doctor. (should / would)
- It’s a holiday tomorrow, so we ___ go to school. (don’t have to / mustn’t)
Answers: 1. must, 2. May, 3. could, 4. should, 5. don’t have to.
Frequently Asked Questions
How many modal verbs are there?
There are nine core modals: can, could, may, might, must, shall, should, will and would. Ought to is often included too.
What is the difference between must and have to?
Both show obligation. Must often shows the speaker’s own feeling; have to often shows an outside rule. In the negative, their meanings are very different.
Can modal verbs be used together?
No. Standard English does not use two modals together, so say will be able to, not will can.
Conclusion
Modal verbs add important shades of meaning to English. Remember the basic rules: modal plus base verb, no -s, and no to (except ought to). Then learn each modal’s main uses with examples.
For more on verbs and grammar, read how to master subject-verb agreement, our guide to understanding and using English grammar, and how to learn English grammar.
