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