English
What are modal verbs, and how do you use them?
Quick answer
Modal verbs (can, could, may, might, must, shall, should, will, would) are helping verbs that add ability, permission, possibility, obligation or advice to a main verb: I can swim.
In one sentence
A modal verb is a helping verb, like can, should or might, that goes before a main verb to show ability, permission, possibility, obligation or advice.
Explained
Compare I swim with I can swim, I should swim and I might swim. The action is the same, but each modal verb changes how we see it: as a skill, as a good idea, or as just a possibility. Modal verbs are a special group of auxiliary (helping) verbs: they never work alone and always need a main verb after them. If you need a reminder about main and helping verbs, see verbs.
bike
umbrella
rain
The nine core modal verbs in English are can, could, may, might, must, shall, should, will and would. Ought to works in the same way, and some longer phrases do a similar job: have to, need to, be able to (sometimes called semi-modals).
Modal verbs follow four simple rules, which make them different from all other verbs:
- No -s for he, she, it. She can, not she cans. This is unusual in the present tense, where most verbs add -s.
- The main verb is in the base form, without to. He must leave, not he must to leave or he must leaves.
- Questions swap the modal and the subject. You can help becomes Can you help? No do is needed.
- Negatives just add not. cannot (can't), could not (couldn't), must not (mustn't), should not (shouldn't), will not (won't).
Modals also show how sure we are. From most to least certain: It will rain → It must be raining (a logical guess) → It should rain → It may rain → It might / could rain. This "degree of possibility" is a key idea in writing, because it lets you sound confident or careful.
Examples
| Meaning | Modal verbs | Example |
|---|---|---|
| Ability | can, could | I can ride a bike. She could read when she was four. |
| Permission | can, may, could | Can I go out? May I open the window? |
| Possibility | may, might, could | It might snow tonight. |
| Obligation | must, have to | You must wear a seatbelt. |
| No obligation | don't have to | You don't have to come, but you can. |
| Prohibition | mustn't, can't | You mustn't touch the oven. |
| Advice | should, ought to | You should drink more water. |
| Future, promises | will, shall | I will call you later. Shall we go? |
| Polite requests | could, would | Could you pass the salt? Would you like tea? |
| Logical deduction | must, can't | The lights are off: they must be out. That can't be right. |
Common mistakes
- Adding -s or to. He cans swim and We must to go are wrong. Say He can swim and We must go.
- Mixing up mustn't and don't have to. You mustn't eat it = it is forbidden. You don't have to eat it = it is not necessary, but you may.
- Putting two modals together. I will can come is wrong in standard English. Use a semi-modal instead: I will be able to come.
- Trying to put must into the past. There is no musted. Use had to: Yesterday I had to walk to school.
Step by step
Step by step
- Decide what you want to sayAbility, permission, possibility, obligation, advice or a request?
- Choose the modalAbility: can/could. Possibility: may/might/could. Obligation: must/have to. Advice: should.
- Add the base verbPut the main verb straight after, with no to and no -s: She should rest.
- Make questions and negativesMove the modal in front of the subject for a question (Should she rest?), or add not after it (She shouldn't rest).
- Check the timeFor the past use could (ability), had to (obligation) or modal + have + past participle: You should have told me.
Practice questions
Using modal verbs
Try each one, then check your answer.
- Choose: She can (swim / to swim / swims).
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Base verb, no to and no -s: swim - Find the modal verb: You should eat more vegetables.
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should - What does can show here? I can ride a bike.
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Ability - Correct the mistake: He cans play the piano.
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He can play the piano. - Correct the mistake: We must to leave now.
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We must leave now. - Turn into a question: You can help me.
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Can you help me? - Make negative: She will come to the party.
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She will not (won't) come to the party. - Which is more certain: It might rain, or It will rain?
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It will rain. - What does it mean? You mustn't run in the corridor.
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It is not allowed (forbidden). - What does it mean? You don't have to wear a uniform.
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It is not necessary, but you may. - Choose the polite way to ask permission: (May / Must) I open the window?
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May - Your friend has a cold. Give advice with should.
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For example: You should rest and drink lots of water. - Put into the past: I can swim. (when I was five)
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I could swim when I was five. - Put into the past: I must finish my homework.
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must has no past form: I had to finish my homework. - Choose: The lights are off. They (must / can't) be out.
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A logical guess that it is true: must - Correct the mistake: I will can help you tomorrow.
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Two modals cannot go together: I will be able to help you tomorrow.
Questions people ask
What are modal verbs in simple words?
They are small helping verbs, such as can, must and might, that go before another verb to show if something is possible, allowed, necessary or a good idea.
What is the list of modal verbs?
The nine core modals are can, could, may, might, must, shall, should, will and would. Ought to is also usually counted, and have to, need to and be able to work in a similar way.
How do you use modal verbs?
Put the modal before the base form of the main verb: I can swim, you should rest, it might rain. Do not add to or -s, and make questions by putting the modal first: Can you swim?
What is the difference between must and have to?
Both show obligation and often mean the same. Must often comes from the speaker (I must call Gran), have to from a rule or outside situation (I have to wear a uniform). In the negative they are very different: mustn't means forbidden, don't have to means not necessary.
Are modal verbs the same in German, Spanish or Italian?
Other languages have modal verbs too, but they behave differently. German has six (können, müssen, dürfen, sollen, wollen, mögen), and they change their endings. In Spanish and Italian, verbs like poder/potere and deber/dovere are normal verbs with full endings, followed by an infinitive.
Is "can I" or "may I" correct?
Both are correct for asking permission. May I is more formal and polite; can I is normal in everyday speech.
Quick quiz
Modal verbs
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Related topics
Verbs
A verb is a word for an action (run, eat, write) or a state of being (is, seem, know). Almost every sentence has one, and verbs change to show tense.
Present tense
The present tense is the verb form for things happening now, things that are always true, and habits, like I walk, she walks or we are walking.
Sentences
A sentence is a group of words that makes complete sense on its own. It starts with a capital letter, ends with a full stop, question mark or exclamation mark, and usually has a verb.
Adjectives
An adjective is a word that describes a noun, telling you what kind, which one or how many, like a huge elephant, a sour lemon or three red balloons.
Adverbs
An adverb gives more information about a verb, adjective or another adverb, telling how, when, where or how often, like slowly, tomorrow, outside or always.
Alliteration
Alliteration is when several words close together start with the same sound, like six silly snakes or big brown bear. It makes writing catchy and memorable.