What are present modals?

They are can, must, may, might, should, and will used to judge something about now: ability, obligation, permission, possibility, advice, or deduction. The form is modal plus a bare infinitive: She can lift the crate. The loft must be occupied. As soon as have plus a participle appears, you have a past modal instead.

How do present modals differ from must have and might have?

Present forms talk about now and drop have: They must be home. Past forms reconstruct a finished event and add have plus a participle: They must have got home. You should radio is advice you can still follow. You should have radioed is criticism of a missed action.

When do I use must and when do I use can't for deduction?

Must plus infinitive is a confident yes about now (The loft must be occupied), and can't plus infinitive is a confident no (The loft can't be empty). Mustn't is the wrong negative here, because it means prohibition: The kettle just clicked; they must be in, but That can't be the skipper; she's in Bergen.

Is will only for the future?

No. Will also makes a present deduction from a cue: There's a knock; that will be the intern. She'll be on the night shift now. The future reading is still the most common, so use context: a knock at the hatch is now; tomorrow is future.

Can I say she cans or she musts?

No: present modals never take -s, never take to before the next verb, and never use does (She can lift it; She must badge in; Can she lift it?). The uniformity is the easy part; choosing which modal fits the job is the rest of the work.

English grammar · Intermediate

Present Modals: Can, Must, May, Might, Should, and Will

Written by Eleanor Whitfield, Lead English Curriculum Editor · Reviewed September 2026

Present modals are can, must, may, might, should, and will used about now: ability (She can lift the crate), obligation (You must sign), possibility (It might jam), advice (You should bleed the radiator), and deduction (That will be the intern). The modal is followed by a bare infinitive, not by have plus a participle. Past judgement uses must have, might have, should have: that is a different page.

The radiator is scalding; the loft must be occupied.

must plus be: a confident deduction about now

What it is

A present modal colours an action or a state that belongs to now, not to a finished past. Can names ability or present possibility. Must names obligation or a confident reading of evidence. May and might name possibility, with might usually weaker. Should names advice or a reasonable expectation. Will, besides the future, names a present deduction (That will be the intern at the hatch). All of them take a bare infinitive: must be, can lift, might jam. As soon as have plus a past participle follows the modal (must have left), you have switched to a past modal and a past judgement.

The lights are on; they must be home. (present deduction) The lights were on; they must have got home. (past deduction: must have plus participle)

How to spot it

Look for a modal plus a base verb with no to and no have: must be, can hear, might stick, should bleed, will be. If have sits between the modal and a participle, leave this page and open past modals. If the meaning is a future plan rather than a now-judgement, you may still be looking at will, but the deduction reading is the present one taught here.

She can hoist that crate on her own. (can: present ability)
You must badge in before you touch the hoist. (must: present obligation)
The hatch might stick in this frost. (might: present or immediate possibility)
That will be the intern with the rota. (will: present deduction from a knock or a shadow)

Have to is a present obligation substitute, not a true modal: it takes to, and it has does and did. Ought to belongs with should in meaning but keeps to. Need as a modal (Need I sign?) is rare in present-day English.

Present Modals Quick Reference

Present modals by job

Job	Modals	Example
Ability now	can (can't)	She can lift the crate. I can't hear the alarm.
Obligation now	must, have to, should (mild)	You must badge in. You should bleed the radiator.
Permission now	can, may	You can leave the hatch ajar. May I sit in?
Possibility now	may, might, could, can	It might jam. It can freeze overnight here.
Advice now	should, ought to	You should radio before you cross.
Expectation now	should	The barge should be at the sandbar by now.
Deduction now	must, will, should; negative: can't	The loft must be occupied. That will be Maya. It can't be empty.
Not past deduction	avoid must have, might have here	They must have left is past; see past modals.

Common Present Modals Examples in English

Present modals grouped by the judgement they make about now:

Ability and Permission

The intern can already splice a line.: can: a present skill
I can't hear the hoist alarm from the loft.: can't: present inability
You can leave your tote on the hatch.: can: informal permission
May I sit in on the briefing?: may: formal permission, present request

Could is past ability or a polite present request (Could I sit in?). As a present-ability statement about now, can is the unmarked choice.

Obligation and Advice

You must sign the berth book before dusk.: must: strong present obligation
We have to bleed the radiators every October.: have to: external rule, present
You should radio the office if the hatch sticks.: should: advice
You mustn't lean on the hoist gate.: mustn't: prohibition, present

Mustn't means do not do this. Don't have to means it is not necessary. That pair is a present-obligation trap and is taught more fully with modals of obligation.

Possibility Now

The spare hatch might still fit.: might: a live, uncertain possibility
It may freeze overnight.: may: possibility, slightly more formal
Frost can buckle a cheap gasket.: can: general present possibility, not a single guess
The barge could already be at the sandbar.: could: present possibility, weaker than must

Might and may guess about now or the immediate future. Can states a known present likelihood. Could sits in between as a tentative guess.

Deduction About Now

The radiator is scalding; the loft must be occupied.: must: confident present deduction
There's a knock; that will be the intern.: will: present deduction from a cue
The barge should be through the sandbar by now.: should: expected present situation
The loft can't be empty; the kettle just clicked.: can't: present deduction that something is impossible

Present deduction uses must / will / should / can't plus a bare infinitive, often be. Past deduction adds have: must have left, can't have forgotten.

How Present Modals Work

One form, a bare infinitive, and a clean split from have plus a participle.

Modal Plus Bare Infinitive

Can, must, may, might, should, and will are followed by the base form with no to and no -s: she can lift, it must be, they might stick. Questions invert the modal: Can she lift it? Must we sign? Negatives attach not to the modal: can't, mustn't, might not, shouldn't. There is no does in a present-modal question or negative.

Must we badge in? You mustn't lean on the gate.

must inverts; not attaches to must

Modal + base form. No to, no does.

Now, Not Then: Drop Have

A present modal judges a present state or action. The pattern is modal plus infinitive: must be home, might jam, should be at the sandbar. A past modal judges a finished event: must have got home, might have jammed, should have radioed. The have is the time marker. If you want now, do not insert it.

They must be home. They must have got home.

be = now; have got = past reconstruction

No have = present. Have + participle = past.

One Modal, Several Jobs

Must is obligation in You must badge in and deduction in The loft must be occupied. Can is ability, permission, and general possibility. Should is advice and expectation. Context, not a label on the word, chooses the job. Deduction often sits with be and with evidence in the other clause (The radiator is scalding; ...).

You must sign. She must be exhausted.

same modal: obligation, then deduction

Read the job from the sentence, not from a single translation.

Can't, Not Mustn't, For Negative Deduction

A confident present deduction in the negative uses can't, not mustn't. The loft can't be empty means the evidence rules emptiness out. You mustn't leave the hatch open is a prohibition, not a deduction. Mixing them is the classic present-modal error from speakers whose language uses one verb for both.

That can't be the skipper; she's in Bergen. You mustn't call her now.

can't = deduction; mustn't = prohibition

Negative deduction = can't. Negative obligation = mustn't.

Common Mistakes with Present Modals

Incorrect: The loft must have occupied now.

Correct: The loft must be occupied now.

A present deduction takes must plus a bare infinitive, usually be. Must have plus a participle is a past deduction and fights with now.

Incorrect: That mustn't be the intern; she's in Bergen.

Correct: That can't be the intern; she's in Bergen.

Negative present deduction uses can't, not mustn't. Mustn't is a prohibition: you are not allowed to. The evidence-rules-it-out meaning is can't.

Incorrect: She cans lift the crate.

Correct: She can lift the crate.

Modals have no -s in the third person and no to before the next verb. Can, must, may, might, should, and will keep one form.

Incorrect: You should to bleed the radiator.

Correct: You should bleed the radiator.

Should takes a bare infinitive. Ought to is the related form that keeps to. Mixing should with to is a blend of the two.

Will and Must for Present Deduction

Two present readings that surprise learners who think will is only future and must is only obligation.

That will be...

Will plus be (or another verb) can mean I deduce this from a present cue: a knock, a shadow, a timetable. It is not a plan.

There's a knock; that will be the intern.: will: present deduction
She'll be on the night shift now.: will be: expected present location
That won't be the skipper; she's in Bergen.: won't: present deduction in the negative, less common than can't

That will be the intern is something you say as the event is happening. That will be the intern tomorrow is a future prediction and a different job.

Must be vs. have to be

For present deduction, must is the modal: She must be exhausted. Have to rarely carries deduction; it carries external obligation: She has to be on site at six. In the negative, deduction is can't, not doesn't have to.

He must be the new skipper; everyone just stood up.: must be: deduction
He has to be on site at six; it's in the rota.: has to: obligation, not a guess
He can't be the new skipper; Maya still holds the papers.: can't be: negative deduction

Mustn't be the new skipper would sound like a prohibition (do not let him be), which is the wrong job.

Should be for expectation

Should plus infinitive can mean I expect this to be true now, not only You ought to.

The barge should be at the sandbar by now.: should: present expectation
The index should be in the crate.: should: I expect it is there
You should be on the night shift, according to the rota.: should: expected present duty

If the expectation failed, English often switches to should have: The barge should have been at the sandbar by now, and it is not.

Quick Check: Present Modals

Choose a present modal, or decide whether the sentence needs have plus a participle instead.

1. The radiator is scalding; the loft ___ occupied. (confident deduction now)

Answer: must be

present deduction: must + be

2. There's a knock; that ___ the intern. (present deduction with will)

Answer: will be

that will be...

3. You ___ lean on the hoist gate. (prohibition)

Answer: mustn't

mustn't, not can't, for a rule

4. That ___ be the skipper; she's in Bergen. (negative deduction)

Answer: can't

can't, not mustn't

5. The lights were on last night; they ___ home. (past deduction: must + have + got)

Answer: must have got

past modal, not present

Present Modals FAQs

What are present modals?: They are can, must, may, might, should, and will used to judge something about now: ability, obligation, permission, possibility, advice, or deduction. The form is modal plus a bare infinitive: She can lift the crate. The loft must be occupied. As soon as have plus a participle appears, you have a past modal instead.
How do present modals differ from must have and might have?: Present forms talk about now and drop have: They must be home. Past forms reconstruct a finished event and add have plus a participle: They must have got home. You should radio is advice you can still follow. You should have radioed is criticism of a missed action.
When do I use must and when do I use can't for deduction?: Must plus infinitive is a confident yes about now (The loft must be occupied), and can't plus infinitive is a confident no (The loft can't be empty). Mustn't is the wrong negative here, because it means prohibition: The kettle just clicked; they must be in, but That can't be the skipper; she's in Bergen.
Is will only for the future?: No. Will also makes a present deduction from a cue: There's a knock; that will be the intern. She'll be on the night shift now. The future reading is still the most common, so use context: a knock at the hatch is now; tomorrow is future.
Can I say she cans or she musts?: No: present modals never take -s, never take to before the next verb, and never use does (She can lift it; She must badge in; Can she lift it?). The uniformity is the easy part; choosing which modal fits the job is the rest of the work.