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

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Dear Kirk, 
LearnEnglish Team.

I have experienced sometimes that when I try to post a comment, it shows "Access Denied" and "You are not authorised to access this page". What is this problem? How can I bypass this problem and post my comments?

Thank you.

Hi ShetuYogme,

As a security measure, the site will log you out if there is no activity (e.g. loading a new page) for a certain period of time. This may happen if you are away from the computer for a while, or if you are writing a long comment, for example. Then you will see this message when you try to post the comment. I'm not exactly sure how long the period is before it logs you out.


LearnEnglish team

Submitted by DoraX on Sat, 07/10/2023 - 10:00


Hello LearnEnglish team,
As I was looking for information about the modal "must", I came across the fact that isn’t common for people to speak to each other about necessity by using the word must, according to a grammar reference source. Is this really the case? If a mother wants her child to be back at 10, won't she say "You must be back at 10." ? Or about homework, "Don't laze around! You must finish your homework."? Or in a work environment between an employer and an employee, isn't "must" used?
In the above situations and in similar ones is it natural to use "must" or "have to" is more commonly used to express obligation in conversation?

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!!!!!