Here is a good activity for modal verbs of possibility.
Use magazines, newspapers, or any material that has images. In partners or groups the students use the pictures to make statements of possibility with modal verbs.
Modals for Possibility:
This person must be rich.
They might be married.
They could be going to a party.
Encourage students to follow up the statements with questions and conversation.
A: He must be a singer.
B: Why do you think that? He could be an actor.
A: No, he is not an actor. He must be a singer, because he is in a concert hall.
This activity is good to practice the modal verbs while speaking. For grammar accuracy, make sure students are following modals with base verbs.
Here is an excellent test for modal verbs of possibility:
Modal Verbs for Possibility Test
Copy and print the test, and then use it with your students. If you would like a lesson for tbhis grammar, try this modal verbs for possibility lesson.