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

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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

Submitted by Oliver Goldwyn on Thu, 25/02/2021 - 08:57

If a sentence says "I missed the school bus. I must or might be late for school?"

Hello Oliver Goldwyn,

In this context you are speculating about the future so the correct choice is might.



The LearnEnglish Team

Submitted by WALTHER on Thu, 14/01/2021 - 01:08

Today I learned the big difference between modal verbs that useful daily, I love with learning English every time... thanks for your support...

Submitted by BobMux on Thu, 31/12/2020 - 12:05

Hello The LearnEnglish Team, Would you please explain me difference between two sentences below? 1.Do not call them now. They must be sleeping. 2.Do not call them now. They can be sleeping now.

Hello BobMux,

To be honest, neither of these sound natural to me, but if I were to use one of them, I'd use 1. If I don't know whether they are sleeping or not, but think that they probably are, I'd say 'Don't call them now. They're probably sleeping' (or perhaps 'They might be sleeping').

I'd use 'they must be sleeping' if, for example, I called them but they didn't answer the phone.

I can't think of a situation when I'd use 'can' here.

All the best,


The LearnEnglish Team

Submitted by Yigido on Sat, 12/12/2020 - 06:40

Hi team, I am confused about this sentence:''Snacks can taste be sweet or salty''Why we use -be-? ''Snacks can taste sweet or salty.''Isn't true?
Profile picture for user Peter M.

Submitted by Peter M. on Sat, 12/12/2020 - 08:18

In reply to by Yigido


Hi Yigido,

That sentence is not correct. As you say, we do not use 'be' here. You could say either of these:

Snacks can taste sweet or salty.

Snacks can be sweet or salty.

I'm not sure, but I think 'savoury' may be a better word here than salty. It would depend on the context, of course.



The LearnEnglish Team