You HAVE TO find more up-to-date information for the report.
You MUSTN'T go past the fence over there.
Lee MAY arrive later, but he's in a traffic jam at the moment.
You DON'T HAVE TO attend the debate if you don't want to.
We AREN'T ABLE to get into the lecture hall yet.
COULD you help me with my CV later, please?
He COULD ski really well before the accident.
She SHOULDN'T take that job because she'll be bored.
You CAN find the details at this website.
They WEREN'T ABLE TO finish the application in time.
possibility
advice / suggestion
obligation
permission / request
ability (past)
lack of obligation / necessity
ability (present, future)
inability (past)
inability (present, future)
prohibition