情态动词本身有一定的词义，表示语气的单词，不能独立作谓语。情态动词主要有can (could), may (might), must, need, ought to, dare(dared), shall(should), will (would)must。

英语情态动词用法顺口溜

情态动词要记牢;动词原形来跟梢。

不管人称单复数;现在过去乐逍遥。

can表能力和许可;也许可能may来表;

必须一定must;should应该来报到。

英语情态动词用法顺口溜

回答不须needn’t;mustn’t为不必要。

否定只要接not;疑问赶紧往前跑。

英语情态动词用法有哪些

can (could),may (might）的用法

can (could) 表示说话人能，可以，同意，准许，以及客观条件许可，could 为 can 的过去式。

Can you pass me the books?你能给我递一下书吗？

Could you help me,please?请问，你能帮助我吗?

What can you do?你能干点什么呢?

Can you be sure?你有把握吗?

can 和could 只能用于现在式和过去式两种时态，将来时态用 be able to 来表示。

He could help us at all.他完全可以帮助我们。

With the teacher's help,I shall be able to speak English correctly.由于老师的帮助，我将能准确地讲英语。

may (might) 可以，表示说话人同意，许可或请求对方许可。

You may take the book home.你可以把书带回家去.

May I come in?我可以进来吗?

May I use your dictionary?我可以用你的词典吗?

You may put on more clothes.你可以多穿点衣服.

He said he might lend us some money.他说他可以借给我们一些钱。

may 否定式为 may not，缩写形式是 mayn't.

might 是may 的过去式，有两种用法，一种表示过去式，一种表示虚拟语气，使语气更加委婉，客气或对可能性的怀疑。

He told me he might be here on time.他说他能按时间来。

Might I borrow some money now.我可以借点钱吗?

He might be alive.他可能还活着。

must,need,ought to,dare (dared）用法

Must 必须，应该，一定，准是，表示说话人认为有必要做某事，命令，要求别人做某事以及对事物的推测。

must 用来指一般现在时和一般将来时，过去式可用 have to 的过去式代替。

I must finish my work today. 我今天必须完成我的工作。

You mustn't work all the time. 你不能老是工作。

Must I return the book tomorrow? 我必须明天还书吗?

After such a long walk,you must be tired. 走了这么长的路，你一定困了。

He must be the man I am looking for. 他一定是我要找的人。

He had to go because of somebody's calling him that day. 那天他要走是因为有人叫他。

must + have + 过去分词，表示现在对过去事物的推测。

He must have told my parents about it.他一定把这件事情告诉我父母亲了。

He must have received my letter now.他现在一定收到我的信了。

It's six o'clock already,we must have been late again.已经六点钟了，我们一定又迟到了。

must 和 have to 的区别：must 表示说话人的主观思想，have to 表示客观需要。

You must do it now.你必需现在就干。（说话人认为必须现在干）

I have to go now.我得走了。（客观条件必须现在走）

need 需要 多用在否定式或疑问句中.

Need I attend the meeting tomorrow?我需要明天参加会议吗?

You need not hand in the paper this week.这一周你不必交论文。

need 是一个情态动词，用法完全和其他情态动词一样，但 need 还可当作实义动词使用，这时 need 就象其他动词一样，有第三人称，单复数，后面加带 to 的动词等特性。

I need a bike to go to school.我上学需要一辆自行车。

Do you need a dictionary?你需要词典吗?

She needs a necklace.她需要一条项链。

needn't + have + 过去分词 表示过去做了没必要做的事情。

You needn't have taken it seriously.这件事情你不必太认真。

dare 敢, 多用在否定或疑问句中。

The little girl dare not speak in public.小女孩不敢在公众面前说话。

Dare you catch the little cat?你敢抓小猫吗?

dare 除用作情态动词外，更多的是当实义动词使用，用法同实义动词一样，要考虑人称，单复数，时态等。

Do you dare to walk in the dark?你敢黑夜走路吗？

He doesn't dare to tell the teacher what happened that day.他不敢告诉老师那天发生的事。

have to,ought ，will ，Shall,should . ought 应当，应该 后面跟带有 to 的动词不定式。

You ought to read these books if you want to know how to repair the motorcar.如果你想知道如何修理汽车，你应该读这些书。

You ought to bring the child here.你应该把孩子带来。

ought + to have done 句型。指过去动作，表示一件事情该做而未做。

You ought to have been here yesterday.你昨天就应该来。

ought not to have done 句型。表示一件不该做的事情却做了。

You ought not to have taken the book out of the reading-room.你不应该把书带出阅览室。

will (would）决心，愿望。would 为 will 的过去式，

可用于各人称。

I'll do my best to catch up with them.我要尽全力赶上他们。

I'll never do it again,that's the last time.我再不会做那件事情了，这是最后一次。

He said he would help me.他说他会帮助我。

will,would用于疑问句表示说话人向对方提出请求或询问，用 would 比 will 更婉转，客气。

It's hot. Will you open the windows?天气太热了，你能打开窗户吗?

Will you help me to work it out?你能帮我解这道题吗?

Would you like some coffee？给你来点咖啡怎样？

Shall,should表示命令，警告，允诺，征求，劝告，建议惊奇。

You should hand in the exercise book.你应该交作业本了。

This should be no problem.这应该没问题。

Shall we go now.我们现在可以走了吗?

Why should I meet him？为什么我要见他?

Shall的用法：

Shall用于第一人称，表示征求对方的意愿。如：

What shall we do this evening?

Shall用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对方请示。如：

Shall we begin our lesson?

When shall he be able to leave the hospital?

Shall用于第二、第三人称，表示说话人给对方命令、警告、允诺或威胁。如：

You shall fail if you don't work harder. （警告）

He shall have the book when I finish reading. （允诺）

He shall be punished. （威胁）

Should的用法：

1． Should表示义务、责任、劝告、建议，其同义词是ought to；在疑问句中，通常用should代替ought to。如：

You should go to class right away.

Should I open the window?

Should的含义较多，用法较活，现介绍三种其特殊用法。请看下面的句子：

① I should think it would be better to try it again. 我倒是认为最好再试一试。

② You are mistaken,I should say. 依我看，你是搞错了。

③ I should advise you not to do that. 我倒是劝你别这样做。

④ This is something I should have liked to ask you. 这是我本来想问你的。

从以上例句可以看出：情态动词should用于第一人称时可以表示说话人的一种谦逊、客气、委婉的语气。

Should还可以用在if引导的条件从句，表示一件事听起来可能性很小，但也不是完全没有可能。相当于“万一”的意思。从句谓语由should加动词原形构成，主句谓语却不一定用虚拟语气。如：

⑤ Ask her to ring me up if you should see her. 你万一见到她，请让她给我打个电话。

⑥ If you should change your mind,please let us know. 万一你改变主意，请通知我们。

⑦ Should I (If I should) be free tomorrow I will come. 万一我明天有时间，我就来。

此外，Why(or How) + should结构表示说话人对某事不能理解，感到意外、惊异等意思。意为“竟会”。如：

⑧ Why should you be so late today? 你几天怎么来得这么晚？

⑨ — Where is Betty living? — 贝蒂住在哪里？

— How should I know? — 我怎么会知道呢？

⑩ I don't know why you should think that I did it. 我真不知道你凭什么认为这件事是我干的。

2． “should + have + 过去分词”结构一般表示义务，表示应该做到而实际上没有做到，并包含一种埋怨、责备的口气。如：She should have finished it.

I should have helped her,but I never could.

You should have started earlier.

3.表示规章制度，用should

will和would

1． 表示请求、建议等，would比will委婉客气。如：

Would you pass me the book?

2． 表示意志、愿望和决心。如：

I will never do that again.

They asked if we would do that again.

3． 用“will be”和“will(would) + have + 过去分词”的结构表示推测，主要用于第二、三人称。前者表示对目前情况的推测，后者表示对已经完成的动作或事态的推测。如：

This will be the book you want.

He will have arrived by now.

The guests would have arrived by that time.

I thought you would have finished this by now.

4．will表示习惯、请求，固有性质等。

Everyday he will sit here hour after hour doing nothing.（习惯）

Will you help me with my English?（请求）

The door won't open. （固有性质）

5．Would可表示过去反复发生的动作或某种倾向。Would表过去习惯时比used to正式，并没有“现已无此习惯”的含义。如：

The wound would not heal.

During the vacation he would visit me every week。

6． 表料想或猜想。如：

It would be about ten when he left home.

What would she be doing there?

I thought he would have told you all about it.

ought to

1．Ought to表示应该。如：

You ought to take care of him.

2．表示推测。注意与must表示推测时的区别：

He must be at home by now. （断定他已到家）

He ought to be home by now. （不十分肯定）

This is where the oil must be. （比较直率）

This is where the oil ought to be. （比较含蓄）

3．“ought to + have + 过去分词”表示过去应做某事而实际未做。如：

You ought to have asked him (but you didn't).

这时，ought to和should可以互相换用。

注意：在美国英语中，ought to用于否定句和疑问句时，to可以省略。如：

Ought you smoke so much?

You oughtn't smoke so much.

ought和should的区别：

1．ought语气略强。

2．should较常用。

3.ought在美国英语中用的很少，而should却相当常用。

4．ought属正式用语。

注：由于ought to 没有过去式，所以在直接引语变间接引语的过程中，就不再变化.