Modal Verbs in English

What Are Modal Verbs?

Modal verbs (also called modal auxiliaries) are a special class of auxiliary verbs that express ability, possibility, permission, obligation, or advice. They differ from regular verbs because they do not take -s in the third person singular, they never appear without a following base verb, and they do not have infinitive or participle forms.

The Main Modal Verbs

• can / could
• may / might
• must
• shall / should
• will / would
• ought to
• need (in some contexts)
• used to

These are the most frequently taught. Semimodals such as have to, be able to, be allowed to behave like regular verbs but convey modal meanings.

Meaning & Function

Ability

Can expresses present ability; could is its past form or a polite request.

Possibility

May and might refer to present or future possibilities; could can also be used for less certain possibilities.

Permission

Use may for formal permission and can for informal contexts. Could often sounds more polite.

Obligation & Advice

Must expresses strong internal obligation; have to denotes external necessity. Should and ought to give advice.

Future & Willingness

Will indicates simple future or willingness; would is its past counterpart and also the polite form of a request.

Key Grammar Rules

1. No -s in third person singular

He can swim, not *cans*. The same rule applies to all modals.

2. Followed by the base form of the verb

Correct: She must go.
Incorrect: *She must goes.*

3. No infinitive or participle forms

We dont say *to can* or *canning*; a modal stays as it is.

4. Negation

Simply add not after the modal (or use the contracted form).

5. Questions

Invert the modal and the subject.

6. Using two modals together

Standard English does not allow two full modals in a row. Instead, use a semimodal or rephrase.

Practice Sentences

Choose the appropriate modal for each blank.

1. _____ (ability, past) You ______ (present permission) use my laptop.
2. It ______ (possibility) rain tonight, so bring an umbrella.
3. Students ______ (obligation) submit their essays by Monday.
4. _____ (polite request) you ______ (future intention) help me move?
5. We ______ (advice) call a doctor if the fever continues.

Answers

• 1. Could / may
• 2. might
• 3. must
• 4. Would / will
• 5. should