Modal Verbs

Modal Verbs

Here is a list of modals with examples:

Modal Verb	Expressing	Example
must	Strong obligation	You must stop when the traffic lights turn red.
must	logical conclusion / Certainty	He must be very tired. He's been working all day long.
must not	prohibition	You must not smoke in the hospital.
can	ability	I can swim.
	permission	Can I use your phone please?
	possibility	Smoking can cause cancer.
could	ability in the past	When I was younger I could run fast.
	polite permission	Excuse me, could I just say something?
	possibility	It could rain tomorrow!
may	permission	May I use your phone please?
may	possibility, probability	It may rain tomorrow!
might	polite permission	Might I suggest an idea?
might	possibility, probability	I might go on holiday to Australia next year.
need not	lack of necessity/absence of obligation	I need not buy tomatoes. There are plenty of tomatoes in the fridge.
should ought to	50 % obligation	I should / ought to see a doctor. I have a terrible headache.
	advice	You should / ought to revise your lessons
	logical conclusion	He should / ought to be very tired. He's been working all day long.
had better	advice	You 'd better revise your lessons

Remember

Modal verbs are followed by an infinitive without "to", also called the bare infinitive.
Examples:
You must stop when the traffic lights turn red.
You should see to the doctor.
There are a lot of tomatoes in the fridge. You need not buy any.