Might, not may is used when the matter was never put to the past.
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Perhaps we should have taken the other food. It might have been quicker.
Could be, can be used instead of may / might be.
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Where is Tom?
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He may / might / could be in the library.
In the interrogative we can use either could or may / might.
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May / could they be waiting for us?
In negative there is a difference in meaning between could and may / might. May / might express the possibility.
Could express negative deduction.
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He may not be driving the car by himself.
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Perhaps he is not driving the car.
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He couldn’t be driving the car by himself.
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This is impossible he cannot drive at all.
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He may not be in Namangan.
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Perhaps he is in Namangan.
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I’m sure he isn’t Namangan.
