4-1 Probability

Modal Verbs

• can
• could
• may
• might
• shall
• should
• will
• would
• must
• ought to

• They do not change forms like other verbs: go, goes, went, gone / look, looks, looked, looked.
• There is no do / does in the question forms. Can you give me a hand?
• There is no don't / doesn't in the negative forms. He shouldn't do that.
• They are always followed by a base form verb. "Ought to" is the only exception as it takes "to" or "not to" before the verb. We would help if we had time. She mustn't do that! We ought to get going.
• They do not usually have past or gerund forms. Other verbs are used instead. I hate having to get up early. (must) I was able to play piano better when I was a child. (can)
• Some modals are used with the Perfect Infinitive to make past forms. This is more explained in Unit 10. You shouldn't have done that. She must have stayed home.

Modal Verbs of Probability: Present and Future