补充：
1.根据情态动词表推测的确信程度大小可作如下排序： must>will>would>ought to>should>can>could>may>might 2.shall的用法：
(1)shall用于一、三人称疑问句中，表示征求对方的同意或向对方请示。
(2)shall用于二、三人称的陈述句中，表示说话人的允诺、保证、命令、威胁、警告、决心或者法律规章上的指示和规定等。 eg: ①Shall I open the window?
②You shall get a new bike you want very much if you get the first prize in the coming exam.
注：shall,will表示命令时的区别。
⑴shall指法律、规章、制度上的“必须”。常用于正式文件中。 ⑵will指责任、义务上的“必须”。常用于日常交际中。 eg:①Each competitor shall wear a number.
②No one will leave the examination room before ten o'clock. 3．should的用法:
⑴表意外，指说话人对某事不能理解，感到意外或惊异，意为“竟然，竟会”。 ⑵表推测，指确定的或可能有的未来或希望，意为“应该”。
⑶表可能，常用在if条件句中，强调某事的可能性，意为“要是，万一”。 eg:①I am surprised that you should speak like that. ②They should be ready by 12:00.
③If he should come,please let me know. 4.would与used to的区别
（1）二者都可表示过去重复的习惯动作。
（2）表示过去的状态，只能用used to,不能用would. （3）used to强调过去与现在的对比，而would只表示过去习惯的动作，常与often、every day等状语连用。
5．含有情态动词的一般疑问句的肯定回答和否定回答。 eg:①------May I sit down?
-------Yes,please./Yes,you may.
②-------Might/Could I use your car tomorrow?
-------Yes,you may/can.或No,you mustn’t/can’t.No,I’m afraid not.
(注：向对方提出请求或建议时，could/might表示语气的委婉，但是在回答时，用can或may。)
③------Must we arrive on time?
------Yes,you must./No you needn’t. ④------Need(必须) I give up smoking? ------Yes,you must./No,you needn’t.
（注：含有情态动词need的一般疑问句作肯定回答，需用must。）
6．will do既可以表示将来时，也可以表示一般现在时，表达习惯性、重复性的动作。区别在于：一般现在时强调“描述性”，而will do强调“预断性”（即：动作如此经常发生，如此具有习惯性或重复性，以致我们可以预断它肯定会继续发生）。
7．can与be able to的区别：
（1）can表示潜在的能力。只有一般现在时和一般过去时两种时态。
（2）be able to表示经过努力而成功地做某事，可用于多种时态。其中was/were able to表示过去有能力并且成功做了某事的能力。
8.must与have to的区别 （1）表示主观上“必须”。只有一种形式。mustn’t意为“不准；禁止；不可以”。 （2）表示客观上“不得不”。有时态、人称等方面的变化。don’t have to意为“不必”。 9.must表示推测时的反意疑问句中的用法。 ①He must be busy now,__________?
②He must have been tired yesterday after a whole day's work,___________? ③He must have been tired ,____________?
10.dare的用法
情态动词dare主要用于否定句、疑问句和条件句，没有人称和数的变化，但是有时态的变化，过去式为dared。 eg:How dare you say so?
dare可用于习惯用语中。 I dare say"我敢说;我认为",表示说话人有把握做出某种判断。
11.may可以用于祈使句中，表达祝愿（其中may和主语常倒装）。 eg:①May you be happy forever.
②May we never forget each other.may与can表示许可的区别 虚拟语气的用法
一． 含义：表示与事实相反或者实现的可能性微乎其微、几乎为零或者表示
一种坚持、命令、要求和建议或者在固定句型中等。 二． 分类：一般虚拟语气和特殊虚拟语气。 三． 用法：
⒈一般虚拟语气的用法 ㈠遵循的原则：
对一般现在时虚拟用一般过去时
对一般过去时虚拟用过去完成时 对过去完成时虚拟用过去完成时 对一般将来时虚拟用过去将来时 „„ ㈡表现形式：
⑴条件句中的虚拟语气。
eg:If he were indoors,he wouldn’t feel cold. ⑵wish后所跟宾语从句中的虚拟语气。
eg:①I wish I were a bird. ②I wish she had taken my advice. ⑶would rather后所跟宾语从句中的虚拟语气。
eg:①I’d rather you paid the money yourself. ②I’d rather she hadn’t done that. ⑷If only（要是„„就好了；但愿）+句子中的虚拟语气。 eg:If only I were a flying bird. If only I had seen the film.
If only Mr. Wang were here now,you would not be punished. ⑸as if/though，even if/though从句中的虚拟语气。（注：在as if引导的从句中，如果从句所说的内容是真实的或可能是真实的，应用真实语气；如果从句所说的内容与事实相反或非真实情况，应用虚拟语气。） eg:①He talks as if he knew all about it.
②Even if he were here,he couldn’t solve the problem. ③He talks as if he were drunk.
⑹含蓄虚拟条件句：介词短语without、but for、otherwise等可替代虚拟条件
句，表达虚拟语气。
注：在对be(am/is/are)动词虚拟时，一律用were来表示。 eg:①But for your help,we couldn’t have succeeded.
②She wasn’t feeling well,otherwise she wouldn’t have left the meeting so early.
⒉特殊虚拟语气的用法
㈠遵循的原则：从句一般用（should）+v原形来表示。 ㈡表现形式：
⑴一坚定二命令三要求四建议，后跟特殊虚拟语气作宾语。（注：insist如果坚持的是一种事实时，应用真实语气；如果坚持的是一种主张时，应用虚拟语气。suggest如果意为“暗示，表明”时，从句应用真实语气。）注：这些动词所对应的名词形式也需用特殊虚拟语气。另外，对应的名词形名词idea等所构成的从句中也应该用虚拟语气。
eg:①He insisted that we (should) take our teacher’s advice.
②The manager demanded that Tom (should) finish it in a week. ③I suggest that you (should) have enough sleep.
④My idea is that we (should) have a meeting to discuss it together. ⑤Our decision is that the meeting (should) be put off. ⑵在句型“It’s important/necessary/essential/vital/proper/right/impossible/strange/natural/a pity/a shame/a surprise/an honor+that从句。”中，that从句要用特殊虚拟语气。
eg:It’s very important that we (should) think before we decide.
但在句型“It’s strange(surprising/unthinkable,etc) +that从句”中，should常译为“竟然”，表示一种不可思议的状况。
eg:It’s surprising that you (should) waste so much time. ⒊虚拟语气的特殊用法
⑴在“It’s (high)time +that从句”中，that从句可用一般虚拟语气或特殊虚拟
语气（should不可省），但二者同时出现时，一般虚拟语气优先使用。 eg: It’s (high)time that he got rid of his bad habit. ⑵if在虚拟条件句中的倒装。
eg:If he came tomorrow,I would tell you as soon as possible.
=If he should come tomorrow,I would tell you as soon as possible. =Should he come tomorrow,I would tell you as soon as possible. =If he were to come tomorrow,I would tell you as soon as possible. =Were he to come tomorrow,I would tell you as soon as possible. ⑶在in case that (以免，免得),lest(唯恐，免得),for fear that ,in order that,so that等引导的目的状语从句
中，that从句要用情态动词(could/might/would/should)+V原形,表示虚拟。 ⑷混合虚拟条件句：
当条件从句与主句所表示的时间并不一致，变为虚拟语气时，可根据它们各自的时态进行变化。
eg:①If I had married her,I would be happy now.
②If you had taken my advice then,you wouldn’t be in trouble now.
③Bring some more money in case you (should) use it later.
⑸had hoped/planned/wanted/expected to do “本希望/计划/想要/期望„„”，可表示过去未曾实现的愿望或打算。
eg:①I had hoped to take his advice.But I didn’t.
②The boy had meant to come in, but the teacher refused him.
⑹在句式“主句主语+vt+that+从句主语+(should) do.”其中主句谓语动词主语urge(极力主张),prefer(宁
愿),desire(请求),maintain(主张),direct(指导)及以上这些动词所对应的其他形式要用虚拟语气。
eg:She preferred that nobody should come to see her.