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情态动词主要用来表示说话人的情感、态度等，是中学英语语法的重点，也是高考的热点，是单项填空必考的一个知识点。情态动词在近五年高考中主要考查四点：情态动词表示推测和可能性的用法；情态动词与虚拟语气；情态动词表达“情感、态度、语气等”；情态动词表示 “必要性”等方面的用法。虚拟语气的考点主要集中在名词性从句、条件句中的用法，以及错综条件句中虚拟语气的应用。
情态动词表推测的用法 情态动词
意义
语气
句式
语境
例句
备注
must 一定
可能性最大
肯定句
对
具
体
事
的判
断 ①A：Look，someone is coming. Who can it be? B: It may be our headmaster. A: It can’t be him. He has gone to Shanghai. B: It must be Mr. Wang. He looks like our headmaster. ②That may not be true. ③He couldn't have discovered the truth.
①对现在的行为或状态的推测：must/may/might/can/could＋do ②对过去的行为或状态的推测：must/may/might/can/could have done
may/might(might可能性小于may) 可能 可能性较小，尤其might最不肯定 肯定句、否定句(可能不)
can/could (could可能性小于can) 可能 疑问句、否定句(不可能)、(could有时也用于肯定句)
有时会 肯定句
情态动词
意义
语气
句式
语境
例句
备注
should /ought to 应该 ，理应
理论上 ①It's 8 o'clock now. He should be in the office now.
②Hi, Mum! I'm on the bus. I should be home in about ten minutes.
常表示在一段时间内可能发生的事或某人的期望。一般句末有时间状语，或有语境暗示。所表示的猜测发生的可能性很大。
注意：should (ought to)表示推测是高考考查的重点和难点。如：
— When can I come for the photos？I need them tomorrow afternoon.
— They ________ be ready by 12：00.
A．can
B．should
C．might
D．need
【解析】 B A项表示推测时常用于否定句和疑问句中。C项表示推测语气不太肯定。should意为“按理说，理应”，既回答了顾客的询问，不失礼貌，又为照片有可能尚未洗好，顾客到时取不到留下了回旋的余地，体现了店主的精明与用词经过仔细推敲。
二、情态动词的其他用法
1．can, could, may, might情态动词 意义
例句
备注
can/could 能力
①I can see some birds flying in the sky.
②Could the girl read before she went to school?
could表示泛指过去的某一能力。表示过去有能力并且成功地做了某事，通常用was/were able to do，相当于managed to do/succeeded in doing。如：Because he practised hard, he was able to pass the driving test.
情态动词 意义
例句
备注
can/could 允许(有时可与may互换)
Can/May I have a look at your photos？
can与could、may与might不表时态差异，只是语气上的差别，could/might比can/may更委婉。注意在回答时不能用could/ might。
请求
—Can/Could you lend me a hand？—Yes, I can.
情态动词 意义
例句
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may/might 允许或请求
①You may take this if you like.
②May/Might I ask for a photo of your baby？
can与could、may与might不表时态差异，只是语气上的差别，could/might比can/may更委婉。注意在回答时不能用could/ might。
2.must, should 情态动词 意义
例句
备注
must
必须
①We must help each other to overcome the difficulties. ②—Must I finish the work today？—No, you needn't/you don't have to./Yes, you must. ③You mustn't take photos here, and it is forbidden.
①must表示主观意志，have to表示客观。如：They had to speed up, for the weather turned terrible. ②Must I/we…？的否定回答不能用mustn't。
偏要
硬要
非要 ①Why must you always interrupt me？
②—Can I borrow your car, Mum？—If you must.
表示与说话人愿望相反及不耐烦。
情态动词 意义
例句
备注
should
应该(常与oughtto通用) You should be polite to the old.
ought to 的否定式：ought not to(oughtn't to)；疑问式：Ought …to…？
竟然
It is strange that he should react in this way.
表示惊讶、意外等语气。
万一
①Should anyone phone, tell them I will call back later. (＝ If anyone should phone…)②If I should go there tomorrow, I would go to see her.
用于if从句中强调“万一”，或用于虚拟语气。
3. need, dare
情态动词 例句
注意事项
need ①I needn't go at once.
②—Need you go at once？—Yes，I must. /No, I needn't. ①need可以作实义动词，用于各种句式。如：I need to go at once.I don't need to go at once. —Do you need to go at once？—Yes，I do.②need作情态动词常用于否定、疑问或条件句中。
dare ①He daren't cross the river.②How dare you say that to me？ dare和need一样，既可以作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句、疑问句和条件句。用作实义动词时，可用于各种句式。如：He didn't dare (to) go out alone at night. (在否定句中to有时可省略)
4.shall/will/would
情态动词 意义
例句
备注
shall
表示征询意见。
Shall I help you？
用于第一、第三人称疑问句中。
表示说话人的意愿，有“命令，允诺，警告，决心”等意思。
①You shall do as I say. (命令)
②You shall have the book tomorrow. (允诺)
③If you don't get out, I shall knock you down. (警告) 用于第二、第三人称。
4.shall/will/would情态动词 意义
例句
备注
will/would 表示意愿
①I will do everything for you. ②None is so blind as those who won't see.
表请求
Will/ Would you please close the window？
用于疑问句中。would更委婉
表示某种倾向或习惯性动作
①Fish will die without water. ②Every time she was in trouble，she would turn to him for help. (would指过去某一段时间的情况，常与表示过去的时间状语连用，意为“总是，总会”，后面只能接动作性的动词。)
used to表示与现在的情况相反，表示“过去如此而现在不再这样”。其后既可接表动作的动词，也可接表状态的动词。如：There used to be an apple tree in front of the house.
4.shall/will/would情态动词 意义
例句
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will/would 表示功能(能，行)
①If you don't have a pen, a pencil will do.②We tried the door again，but it wouldn't open.
与否定词连用常表示“拒绝”。
表示推测(可能、大概)
①This will be the house you are looking for. ②I would be about ten when my father left home.
情态动词＋have done 情态动词 意义
例句
备注
must have done；may/might have done；can/could have done 一定(肯定句)；可能(肯定句和否定句)；可能(疑问句和否定句) You can't/couldn't have met my grandmother. She died before you were born.
对过去的事情的推测
might have done; couldhave done；would have done 本来可能做……而未做；本可以做……而未做；本来会做……而未做 ①He might have given you more help, even though he was very busy.②We could have walked there, and it was so near. 与过去事实相反的虚拟表达
情态动词 意义
例句
备注
should/ought to have done 本应该做……而未做
Your brother has failed English exam again. You ought to have given him more help.
表示责备
needn't have done 本不需要做……但却做了 You needn't have wakened me up; I don't have to go to work today.
四、虚拟语气
虚拟语气表示说话人所说的话不是事实，而是一种假设、愿望、怀疑或推测。
虚拟语气在条件句中的用法 if从句 主句
与现在事实相反 if＋主语＋动词过去式 主语＋should/would/could/might＋动词原形
与过去事实相反 If ＋主语＋had＋过去分词 主语＋should/would/could/might＋ have＋ 过去分词
与将来事实相反 (1) if＋主语＋动词过去式 主语＋should/would/could/ might＋动词原形
(2)if＋主语＋were to＋动词原形
(3) if＋主语＋should＋动词原形
If it were to rain tomorrow, I should not drive my car. 如果明天下雨的话，我就不开车了。(明天的情况还不知道)
If I had done it in time, I should have had a good time. 如果我及时做的话，日子就好过多了。(可惜当时没能及时做)
注意：
(1) 主句中的should通常用于第一人称，would可用于任何人称。
(2) 条件句中如果动词是be，其过去式所有人称的单复数都可用were；在第一、三人称单数的口语中，可用was代替were。但在if I were you中，不能说成if I was you。
(3) 当条件从句的行为与主句所表示的行为所发生的时间不一致时，主从句中动词的形式要根据它所标示的时间作出相应的调整，这就是所谓的“错综条件虚拟语气”。如：
If they had studied hard, they could do it easily now.
如果他们以前努力学习的话，现在干得就会容易些了。
If he had not taken my advice, he wouldn't do it much better like this.
如果他不听我的建议，他就不会干得这么好了。
(4) 在条件句中，如果有were, had, should等，则可省略if，但应注意把were, had, should等提到从句主语之前。
如：If he were to come, I would join him in the discussion. ＝ Were he to come, I would join him in the discussion. 如果他来，我将和他一道参加讨论。
(5) 有些虚拟条件句没有从句，虚拟条件句是通过上下文或介词短语表示出来的。如：
But for air and water, there would be no life on the earth. 要是没有空气和水，地球上就没有生命。(介词短语but for提供了虚拟条件)
With your help, we might finish the plan earlier. 要是有你的帮助，我们就可以早些完成任务。(介词短语with your help充当虚拟条件句)
2． 虚拟语气在wish从句中的用法
专题八 │ 正面解读
宾语从句 愿望
I wish
主语＋动词过去式 现在不能实现的愿望
主语＋had＋过去分词 过去不能实现的愿望
主语＋would/might＋动词原形 将来不能实现的愿望
I wish I were a doctor. 我希望我是个医生就好了。(现在)
I wish that the rain would stop. 我希望雨能停下来。(将来)
I wish that he had not made so much fuss about it.
我希望他不要把事情搞大了。(过去)
3． 虚拟语气在名词性从句中的使用
(1) 在insist；command，order；demand，request，require，desire；advise, propose, suggest，recommend等表示“命令、要求、建议”的动词后接的宾语从句中要使用虚拟语气。如：
He suggests that she (should) leave the house at once.
他要她立刻离开这所房子。
He proposed that we (should) deal with the problem by the view of development.
他建议我们应该用发展的眼光处理这个问题。
(2) 与上述动词相对应的名词suggestion, order, demand , proposal 等后的表语从句、同位语从句中也要使用虚拟语气(should可省略)。如：
My proposal is that we (should) set a deadline for handing in the plan.
我的建议是为这个计划设定一个上交的期限。
(3) 在It be suggested (ordered, demanded, proposed, … )that… 结构中，主语从句中也要使用虚拟语气。如：
It's required that every student be on time for school.
要求每个学生准时到校。
(4) 在do you suggest/recommend用在特殊疑问句中作插入语时，句子的动词也使用虚拟语气，即“should＋动词原形”的形式，其中should可以省略。如：
What type of computer do you recommend/ suggest we (should) buy?
你建议我们买什么类型的电脑呢？
(5) 在It's＋necessary，essential，important, strange, natural等形容词＋ that从句或It's a pity，a shame等名词＋ that 从句中，谓语动词可以使用should do。如：
It is necessary that the badly wounded man should be treated immediately. 这位重伤员必须马上治疗。
It's a pity that you should be so careless.
你竟然如此粗心，真是可惜。
4． 虚拟语气在状语从句中的用法
在as if/though引导的状语从句中，谓语动词用过去式表示与现在相反的情况；用过去完成式，表示与过去相反的情况等。其变化与wish后的宾语从句的变化相同。如：
I've loved you as if you were my relative.
我一直爱你仿佛你是我的亲人。
5． 虚拟语气在其他一些句型中的用法
(1) It's high time that从句中，谓语动词可以使用过去式，也可使用should＋动词原形；表示“早该……了”，其中should不可省略。如：
It's high time we got up/should get up. 我们早该起床了。
(2) would rather＋从句中，谓语动词用过去式表示与现在或将来的情况相反；用过去完成式，表示与过去的情况相反。如：
I would rather you came tomorrow. 我宁愿你明天来。
(3) if only…要是……多好啊。如：
If only you hadn't offended him. 你当时不惹他就好了。
If only he could come tomorrow. 他明天能来就好了。
