Modal verbs
Modal verbs are auxiliary verbs, such as can, could, may, might, must, shall, should, will and would, that combine with a main verb to express ideas like ability, permission, possibility, obligation or advice. They do not change form for person or tense and are followed directly by the base form of the verb, without "to".
Types of modal verbs
Ability
Express what someone is or was capable of doing.
e.g. can swim, could speak French as a child
Permission
Ask for or give permission to do something.
e.g. may I leave?, you can park here
Possibility and speculation
Show how certain or uncertain something is.
e.g. it might rain, she could be at home, he must be tired
Obligation and necessity
Express duty, rules or things that are required.
e.g. you must wear a seatbelt, students should attend all classes
Advice and suggestion
Recommend a course of action.
e.g. you should apologise, you ought to see a doctor
Rules to remember
- A modal verb is always followed by the base form of the main verb, with no 'to' (except 'ought to'): 'She can drive', not 'She can to drive'.
- Modal verbs never change form: no -s, -ing or -ed endings, even with third person singular subjects (he can, not he cans).
- Negatives are formed by adding 'not' directly after the modal: cannot, must not, should not.
- Questions are formed by inverting the modal and the subject: 'Can you help me?' not 'Do you can help me?'
- Modal verbs have no infinitive or participle form, so other expressions like 'be able to' or 'have to' are used to fill gaps in tense or form.
Examples in sentences
| Example | How it works |
|---|---|
| I can speak three languages. | Expresses present ability. |
| You must submit the form before Friday. | Expresses a strong obligation. |
| It might rain later, so take an umbrella. | Expresses possibility. |
| Could I ask you a question? | Makes a polite request. |
| Students should revise regularly for the exam. | Gives advice or recommendation. |
| He must be exhausted after that flight. | Expresses confident speculation about the present. |
| We could not find the address. | Expresses past inability using the negative form. |
Common mistakes
Incorrect: She cans drive very well.
Correct: She can drive very well.
Incorrect: You must to finish your homework.
Correct: You must finish your homework.
Incorrect: He will can help you tomorrow.
Correct: He will be able to help you tomorrow.
Why this matters for IELTS
Using a range of modal verbs accurately, rather than repeating "can" and "must", shows the grammatical flexibility examiners reward under Grammatical Range and Accuracy. In Speaking and Writing, modals like "might", "could" and "should" let you hedge opinions, speculate and give balanced recommendations, which is essential for Task 2 essays and Part 3 discussions where nuanced, well-supported opinions raise your band score.
Frequently asked questions
What are modal verbs in English?
They are auxiliary verbs such as can, could, may, might, must, shall, should, will and would that add meaning like ability, permission, possibility or obligation to a main verb, and they never change form.
Do modal verbs take an 's' after he, she or it?
No. Modal verbs never add -s, so it is 'he can', 'she must', 'it will', never 'cans', 'musts' or 'wills'.
What is the difference between 'must' and 'have to'?
'Must' often expresses the speaker's own authority or strong personal obligation, while 'have to' usually refers to an external rule or requirement, though in many everyday contexts they are used interchangeably.
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