Modals: deductions about the present

Modals: deductions about the present

Do you know how to use modal verbs to say how certain you are about a possibility? Test what you know with interactive exercises and read the explanation to help you.

Look at these examples to see how must, might, may, could and can't can be used.

That must be the main entrance. I can see people queuing to get in.
I've lost my keys. They might be at work or they could be in the car.
You can't be bored already! You've only been here five minutes. 

Try this exercise to test your grammar.

Grammar test 1

Modals – deduction (present): Grammar test 1

Read the explanation to learn more.

Grammar explanation

We can use modal verbs for deduction – guessing if something is true using the available information. The modal verb we choose shows how certain we are about the possibility. This page focuses on making deductions about the present or future. 


We use must when we feel sure that something is true or it's the only realistic possibility.

This must be her house. I can see her car in the garage.
He must live near here because he always walks to work.
Come inside and get warm. You must be freezing out there!

might, may, could

We use might, may or could to say that we think something is possible but we're not sure. 

She's not here yet. She might be stuck in traffic.
He's not answering. He could be in class.
We regret to inform you that some services may be delayed due to the bad weather.

They all have the same meaning, but may is more formal than might and could.


We use can't when we feel sure that something is not possible.

It can't be far now. We've been driving for hours.
She can't know about the complaint. She's promoted him to team leader.
It can't be easy for him, looking after three kids on his own.

Note that these verbs, like all modal verbs, are followed by an infinitive without to.

Do this exercise to test your grammar again.

Grammar test 2

Modals – deduction (present): Grammar test 2

Language level

Average: 4.2 (54 votes)

Hello DoraX,

I wouldn't go too far with this but I think in everyday speech 'have to' is much more common. 'Must' can sound a little more formal. That said, 'must' is perfectly natural and correct as an alternative.


I think part of the issue is that a lot of non-native speakers of English have a similar word to 'must' in their languages and sometimes see 'must' as an equivalent, so end up overusing it. It's not a huge issue, however, and over time as you listen and read you'll pick up these kinds of tendencies. That's really the way to approach it rather than through rules.



The LearnEnglish Team

Submitted by julbaluk on Tue, 03/10/2023 - 18:41


I am puzzled by an example on another page of British Council.
and this is the example:
Question: 'Mark's son started a new school last month. He doesn't like it at all.'
Answer: ' Well, moving to a new school can be really difficult.'
Is it correct to use 'can' here to make a deduction?
Or is it more appropriate to use 'must' here?

Thank you in advance.

Hello julbaluk,

You are right in thinking that we don't use 'can' to make a deduction. In this case, 'can' is used to make a general statement about what is possible.

It is grammatically correct to use 'must' instead of 'can' here, but it changes the meaning of the sentence -- instead of making a general statement about what moving to a new school often is like, it makes a deduction. It can certainly be appropriate to say this.

Does that make sense?

All the best,
LearnEnglish team

Submitted by svetla_79 on Thu, 28/09/2023 - 12:42


Hi, team! Is might past tense of may?

Hello svetla_79,

In older styles of English, 'might' is indeed the past form of 'may'. But that doesn't describe very well how the two forms are used nowadays. If you want to talk about past possibility, for example, you could use 'may have' or 'might have'.

I'd suggest you have a look at our 'may' and 'might' page, where the most common uses of both forms are explained in more detail. Please feel free to ask us any further questions there if you like.

All the best,
LearnEnglish team

Submitted by howtosay_ on Sat, 07/01/2023 - 17:12



Could you please help me with this issue:

If I, for example has fixed my sink, could I say "It has to be better now" or "It must be better" is the only correct variant? As I understand, we never use "have to" for deductions, but I'm not certain.

I very appreciate your work and thank you very much for answering this post!!!!!

Hello howtosay_,

You can use either form for deductions. Must is more common, but it's possible to use have to when you want to express a strong conviction:

Paul must be tired. He's just finished a marathon!

Paul has to be tired. He's just finished a marathon!



The LearnEnglish Team

Profile picture for user Ahmed Imam

Submitted by Ahmed Imam on Tue, 22/11/2022 - 09:26


Hello. Could you please help me? I think both give suitable meaning.
- He (must be - can't be) cold. He isn't wearing a jacket.
Thank you.

Hello Ahmed Imam,

Both are possible but show the speaker has a different perception. 'He must be cold' means the speaker thinks the man is cold; 'He can't be cold' means the speaker thinks he is not cold.

Does that make sense?

All the best,
The LearnEnglish Team