Using Modals in Past Tense, Concept and Example Sentences

Modal	Concept	Example
Would have	Past unreal action	If I had guessed the future, I would have taken some precautions against what would happen.
Could have	Past unreal ability	He could have taken the flight.
May have	Past unreal possibility	We may have passed the math exam, but it was in Spanish.
Might have	Past unreal small probability	You might have sold the car., if you really needed the Money.
Should have	Past unreal recommendation	You should have listened to the teacher.
Must have	Past unreal assumption	We must have been crazy!