Modal verbs of deduction

​Must, may, might, could and can't

We can use modal verbs of deduction to express how sure we are about something happening in the present or the future.​

​We use must when we feel sure about something because there is some kind of evidence.

​You have been working all day. You must be very tired.

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Come inside and get warm you must be freezing out there.

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​We use can't when we feel sure somehing is not true.

​You have been sleeping all day. You can't be tired.

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They can't be poor because they have an incredible house and four cars. 

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We use may, might and could when are not sure about something, but we think it is possible.

She might go to the party tomorrow if you ask her. 

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Peter could be at the library. He said he was going to go one of these days.

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They may win the match. They are quite good.​

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​Form

​Subject + modal verb of deduction + Bare infinitive

​It must be the postman.

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​Subject + modal verb of deduction + be + verb-ing

​She might be having a bath.

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