Modals of possibility and certainty

May, might, can, could, must:

We use may, may not, might, might not and could to talk about present or future possibility.

• My date with Ben could be a disaster.
• We might have nothing in common.
• They could be on the train now.
• You may get on really well.

We use can't when we believe or guess that something is impossible.

• He can't be boring-he's in a band!.

We use must when we are certain something is true.

• He must be a nice person if he's Jeff's friend.

We use must and can't when we make logical deductions.

• That must be his brother- they look alike.
• Linda can't be at home because she didn't answer the phone.