Modals

Words like can, will, may, must, and a few others are called modals. Modal auxiliary verbs help other verbs express a meaning or an idea. Some common uses of the modals are these:

　　　　　Ability: He can speak English now.

　　　　　　　　He couldn't speak English a year ago.

　　　　　　　　I'm not able to come to the game on Friday.

　　　Permission: All passengers may now board.

　　　　　　　　We can board now.

　　　Obligation: You must fasten your seat belts. (strong)

　　　　　　　　　You should pay attention.

　　　　　　　　　 (weak)

　　　　　　　　You out to pay attention.

　　　　Possibility: It may rain.

　　　　　　　　　How could I forget an import thing like that?

　　　　　　　　　He can't /must have known the result.

Meanings similar to those of the modals can often be conveyed by real verb forms:

　He has to =...must...

　　　is able to speak English. =...can...

　　　is allowed to =...may...

　　　is supposed to =...should... (be) able to ability, less used than can

e.g. I'm not able to come to the game on Friday. can

ability

e.g. Can you play the piano? asking for and giving permission

e.g. "Mom, can I go the cinema tonight?"

"No, you can't. You have homework to do" offer

e.g. Can I help you? request, instruction

e.g. Can you switch on the light for me?