参考：无忧英语51talk梁颖老师的超实用语法20讲在线课程第15 16 17课
lesson 15 16 17情态动词modal verb
(1)A：Hey,you! open this door.
B: it's locked. want me get the key.
A: Yeah. get it. Fast!
(2)A:Excuse me, would you please open this door?
B: I'm afraid it's locked. shall I get a key?
A: Please, if you would't mind, as quickly as you can.
(3)he swims well.
he can swim well.
he may swim.
I should swim.
I must swim.
I will swim.
一、情态动词综述
情态动词特点
1.情态动词后用动词原形
he can swim very well.
2.否定not直接跟着情态动词
he can not swim.
3.疑问语序：情+主+动
can he swim?
情态动词有哪些情绪呢？
推测
请求
命令
建议
情态动词有哪些？
情态动词
现在式 过去式 短语
can could be able to
may might be allowed to
must have to
shall should ought to
will would be going to
二、情态动词详解
1.can/could
1.1能，有能力做， could是can的过去时
she can play the piano.
she could play the piano at the age of 5.
I could kill you with my thumb.
Anybody can make mistakes.
1.2客观可能
can表示客观上可能50%， could表可能40%
he could be a detective.
the king lion
the past can hurt.
you can't change the past.
but I think you can either run from it or learn from it.
Fear can hold you prisoner. hope can set you free. a strong man can save himself. a great man can save another.
one of the few things you could say about english people with certainty is that they talk a lot about the weather.
1.3can/could用在否定句和疑问句
表否定推测90%，could的语气理弱
it must be fake.
it can't be real. it must be fake.
could it be real?
1.4can/could表请求/许可（非正式），could更委婉
此时否定can't表示禁止
--can I have a look at your book?
--yes, of course you can.
you need to get a license before you can drive a car in this country.
you can borrow my notes provided you take care of them, I told my friends.
you can't take your camera into the museum.
2.may/might
2.1表示请求/许可（正式）
might更委婉
may not表不同意、拒绝
--May I see you back to the village?
--No.
--May I dance with you?
--yes, you may.
--Can I leave the table now?
--I'm sure you can, but you may not.
you may not sleep immediately after you have your dinner.
2.2表示祝愿
long may you live.
May the road rise up to meet you.祝你一路顺风
may heaven protect you
may our friendship live long.
happy may your birthday be!
may the force be with you.
May you never steal, lie or cheat.
But if you must steal, then steal away my sorrow.
it you must lie, lie with me all the nights of my life.
and if you must cheat, then please cheat death because I couldn't live a day without you.
2.3表示推测、可能性
may 40%, might 30%
she may come or she might not.
I thought I might lose you.
2.4 may/might as well 不妨
you may as well eat something at midnight.
this TV program is quite boring we might as well listen to the music.
3.must
3.1必须、一定要！（主观）
mustn't 表禁止
I must learn another language.主观想法=I want to--
You must be back before 10 o'clock叮嘱或命令=I want you to--
She must do it herself.说话人的意志=I want her to--
--Must I come back before ten?
--yes, you must
--No, you needn't.
3.2一定、准是！表非常肯定的推测
there must be a mistake.
it may be a wolf.
It must be a Husky.
the restaurant must be very good. it's always full of people.
the restaurant may not(不确定答案是否对） be very good. it's always empty.
you got here very quickly. you must have walked very fast.
Bill has bought 4 cars. he must be short of money.
which of the following sentences express "probability"?
A. you must leave immediately.
B.You must be feeling rather tired.
C.You must be here by eight o'clock.
D.You must complete the reading assignment on time.
After I gave her my advice, she must go and do the opposite.
3.3偏要
the rain was bad enough, then it must snow. (can/must/may/might)
Why must I give up my dream?
4. will/would
I can, I will, end of story.
4.1表意愿！意志！决心
would是will的过去式
I will finish my work even if I have to stay up all night.
he said he would do anything for her.
4.2请求、建议（疑问句），would更委婉
can you maybe show me how to make more money with this? of course I could.
will you?
Would you accompany me to the lake this afternoon? Yes , I would be delighted.
Would you mind if I did--
Would you mind if I used your phone?
Would you mind if I talked with her for a while /first ?
Would you mind if I ate this cookie?
4.3习惯，will表现在，would表过去
this old man is strange. he will sit for hours without saying anything every day.
Last year she would go to the orphange on sundays.
5.shall
5.1在含有第一、第三人称的疑问句中表征求意见、请示
Shall we put off the sports meeting until next week?
5.2在含有第二、第三人称的句子中，表：许诺、命令、警告、威胁
tell Jack he shall get a gift if he is nice.
--Will you read me a story, Mummy?
--OK, you shall have one if you to to bed as soon as possible.
5.3在含有第三人称的句子中，表示义务：应该、必须
Those belonging to our club shall wear uniforms.
--What does the sign over there read?
--"no person shall smoke in this area."
It has been annouced that candidates shall remain in their seats until all the papers have been collected.
6.should
6.1义务、职责、应该
one should love animals. they are so tasty.
that should be a matter of concern in a presidential election year.
6.2推测：按道理应该70%
it's already 10.
she promised to come by 10.
she should be here at any moment.
6.3惊奇、愤怒、失望
it's astonishing that she should kill her own husband.
I am surprised that you should think the city is a dull place to live in.
情太动词表推测
从100%--0%
he is sick
he must be sick
he should be sick
he could be sick
he may be sick
he might be sick
he can't be sick
he isn't sick.
yes, I did it!
I will do it
I can do it
I'll try to do it
how do I do it?
I want to do it
I can't do it
I won't do it.
which step have you reached today?
半情态动词
既可以当情态动词could+，也可以当实义动词want+
7.need
需要、必要
情态动词
常用在否定或疑问中
--Need I tell him everything that has happened to his parents?
--No, you needn't/ Yes, you must.
you needn't tell her the truth.
need作实义动词
I need to buy a couple of books.
I needn't feel sorry for you.
I need to finish it in time.
do you need to leave now?
need I wait for you?
I don't need to work hard.
8.dare (dared)
敢！
常用在否定句、疑问句、条件句中
Dare you take this 5-storied bus for sightseeing?
he dare not speak in front of his teacher.
dare实义动词
we must dare to think, speak, and act!
常用的情态动词用法比较
1.can 与be able to
the light bulb can save energy.
1)be able to 不用于物
the can can get the speed of 200 miles/hour.
she couldn't climb the mountain.(没有能力爬，因而没爬）
She was not able to climb the mountain.（尝试爬过，但没能爬上去）
2)一般用was/were able to 叙述过去经过努力才能完成
after 6 months of learning, I was able to play the piano finally.
I could play the piano at 6.
3)be able to 有各种时态
I'm sorry I haven't been able to answer your letter in time.
I couldn't leave before you came. I had not been able to leave before you came.
can you take you camera tomorrow? will you be able to take your camera?
2.must 与 have to
1)must主观，have to客观
I must learn another language.
I have to learn another language.
2)have to 有多种时态变化
Bill starts work at 5 a.m. he has to get up at four.
I broke my arm last week. Did you have to go to hospital?
there was a lot of noise from the street. we had to close the window.
Karen can't stay for the whole meeting. She has to leave early.
How old have you been to drive in your country?
I don't have much time. I have to go soon.
How is Paul enjoying his new job? he has to travel a lot.
I'm afraid I can't stay long. What time have you stay?
the bus was late again. how long have you been wait?
there was nobody to help me. I had to do everything by myself.
3.would VS used to
过去常常
would客观描述过去常发生的事情
used to 过去的习惯动作或状态，强调现在已不存在
Man used to think that the earth was flat.
He would read deep into the night.
would可表示不规则习惯，used to不行
sometimes she would take a walk in the neighboring woods.