You don’t have to wear your school uniform tomorrow.
no obligation
The skiing trip will be a success, I’m sure.
certainty
They didn’t have to do their homework until Friday.
no obligation (past)
I must go to the supermarket today to get Tim’s present.
obligation
May I close the window, please?
permission
Luke ought not to drive so fast.
advice
We mustn’t wear jewellery in school.
prohibition
You can finish this essay after class.
permission
Sara was not to drive the car without her father
prohibition
Would you buy me a newspaper while you’re out, please?
requests
Laura had to go to the bank yesterday.
obligation (past)
Diane can play the piano very well
ability
I may start a new course next year.
possibility
Amy could have spoken fluent German (if she had stayed in Bonn for longer).
possibility
The car should be fixed by now.
likelihood
Mary should have gone alone.
advice
Fred won’t be able to get here until Sunday
ability