Overview of Modals and Related Expressions
1.The modal verbs are can, could, shall, should, will, would, may, might, and must. Subject+ modal+ basic verb(动词原形)
She should leave. ( Advice)
She must leave.( necessity)
She might /may / could leave. ( possibility)
2.To form the negative, put not after the modal.
You should not leave now.
He cannot speak English. ( Cannot is written as one word)
3. A modal can be used in passive voice. ( Modal +be+ past participle) A pen should be used for the test.
The movie can be seen next week.
4. The following expressions are like modals in meaning: have to, have got to, be able to , be supposed to, be allowed to, be permitted to, had better. He must go to court.= He has to go to court.
You must not park your car there.= You are not supposed to park your car there. He can speak English well.= He is able to speak English well. 5. Don’t use two modals together.
You will have to go to court. ( right)
You will must go to court. ( wrong)
6. Don’t use an infinitive after a modal.
He must be gone. ( right)
He must to be gone. ( wrong)
@Note: For the future tense, shall is more common in British English than in American English. Americans sometimes use shall in a question to make a suggestion or invitation. Example: Shall we dance?
British: (a) We shall study modals. (a) I shall see you tomorrow. American: (b) We will study modals. (b) I will see you tomorrow.
1. Social acceptability
Students in the U.S. can wear jeans to class.
2. Suggestions ( can/ could), Can and could are used to offer suggestions when more than one choice is acceptable. (Can and could have the same meaning in offering suggestions. Could does not have a past meaning in offering suggestions.) I get annoying telemarketing calls. What could/can I do?
You could/can listen politely, or you can say you’re not interested and hand up. You can/ could have them send you information by mail.
Possibilities --- May, Might, Could
1. We use may,might, and could to show possibilities about the present or future . Use already, and now with the modals to emphasize present possibility. In the future possibility, the outcome is not certain. (may= might= could)
You are a winner. ( certain)
You may already be a winner. ( uncertain) ( present possibility) Future:
You will win a prize. ( certain)
You might/could/ may win a prize. ( uncertain) ( future possibility) She looks confused. She might/could/ may not know the answer. She might/could/ may not understand the question. ( present possibility) This could be your lucky day! ( future possibility)
2. For negative possibility, use may not or might not. Don’t use could not. It means was/ were not able to. Do not make a contraction with may not or might not. She may not know that she is a winner.
Ex: Some people might not understand the conditions of a sweepstakes.
3. To make questions about possibility with may, might, could, say, “Do you think…may, might, could…?” The clause after Do you think uses statement word order( noun clause). Ex: Do you think I might win?
Do you think I could get lucky?
4. Maybe, written as one word ( a), is an adverb. It is usually put before the subject. May be, written as two words (b), is a modal+verb. The meaning of (a) and (b) are the same, but notice that the word order is different.
Wrong: He maybe is a winner.
(a) Maybe you are right. = (b)You may be right.
(a) Maybe he is a winner.= (b) He may be a winner.
Necessity and urgency with must, have to, have got to
1. For legal obligation, use must and have to. Must has a very official tone. It is often used in court, in legal contracts ( such as rental agreements), and in rule books ( such as a book of driving rules and laws). （必须） Individuals and companies must ( or have to )obey the law.