因为不晓得楼主什么学段的，自以为是的粘了个高中段的，不知道合适不，结合题看吧，这种东西语感也很重要，理论的东西看太多也无法比较的。有不懂的楼主可以继续问我a，我会尽力的。
ps：转自Susan的博客~~~
从高考看英语情态动词用法
一 表示能力,陈述事实
Can，could, be able to
1、 can (could)，用在现在时和过去式中，其他时态要用be able to的形式
Black holes ______ not be seen directly, so determining the number of them is a tough task.(2006上海)
A can B should C must D need
You know he is not going to let us leave early if we ______ get the work done. (2006上海)
A can’t B may not C shouldn’t D mustn’t
Peter ______ be really difficult sometimes even though he is a nice person in general.(2008辽宁)
A shall B should C can D need
【答案】A A C
2、 Was/were able to 可以表示成功做成某事的含义
【例】With our help, he was able to build the house. 在我们的帮助下，他得以建成这座房子。
Jimmy could talk for hours without getting tired. But last night he was not able to utter a word for he got a boil in his tongue.
Jimmy可以滔滔不绝地说上好几个小时。但是昨天他一个字也说不出来，因为舌头上长了个泡。
二 表示请求或许可
Can，could
这两个词可以用于所有人称，只是Could 比 Can 更加客气。
【例】Could I have a word with you, please?
我能跟你说点事吗？
will and would
这两个词专属第二人称，只是would 比will 更客气委婉。
【例】Close the door when you leave, will you?
离开时记得关门，好么？
Would you mind closing the window? It’s cold here.
麻烦关一下窗好么？这里冷得很。
--Write to me when you get there.
--________.(2001全国春)
A I must B I should C I will D I can
【答案】C
Shall
Shall表建议时用于第一第三人称
--The room is dirty. ______ we clean it?
--Of course. (2003北京春)
A Will B Shall C Would D Do
【答案】B
三 表示推测或可能性:
这种情况下，情态动词后面接的动词，分以下两种情况：
对现在的推测：情态动词+动词原形
对过去的推测：情态动词+动词的完成式（即have done）
Can, could
常用于否定句和疑问句
My English-Chines dictionary has disappeared. Who _____ have taken it?(2003上海春)
A should B must C could D would
You ______ be hungry already—you had lunch only two hours ago! (2008浙江)
A wouldn’t B can’t C mustn’t D needn’t
【答案】C B
may and might
这一组词表示轻微的推测，说话人不是很肯定，might比may不肯定的语气更加强烈。
You might just as well tell the manufacturer that male customers ____ not like the design of the furniture. (2004上海春)
A must B shall C may D need
Although this ______ sound like a simple task, great care is needed.（2008四川）
A must B may C shall D should
Liza ____ well not want to go on the trip—she hates travelling.(2008全国Ⅱ)
A will B can C must D may
【答案】C B D
must
表示推测，意思非常肯定
--Guess what! I have got A for my term paper.
--Great! You _____ read widely and put a lot of work in it.(2007上海)
A must B should C must have D should have
【答案】C
Should， ought to(表示如果不这样，有点不合常理之意)
There _____ be any difficulty about passing the road test since you have practiced a lot in the driving school. (2005上海)
A mustn’t B shan’t C shouldn’t D needn’t
【答案】C
四 表示必须
Must， have to
可以互换，只不过have to有多种时态。同时，两个词的否定式意义有区别，Mustn’t 表示禁止，Don’t have to表示不必要，等于needn’t。
According to the local regulation, anyone who intends to take a driver’s license ____ take an eye test. (2005上海春)
A can B must C would D may
When I was young, I was told that I ______ play with matches. (2008上海春)
A wouldn’t B needn’t C mustn’t D daren’t
The boss has given everyone a special holiday, so we _______ go to work tomorrow. (2007上海春)
A can’t B mustn’t C needn’t D shouldn’t
--What do you think we can do for our aged parents?
--You ________ do anything except to be with them and be yourself.(2007重庆)
A don’t have to B oughtn’t to C mustn’t D can’t
【答案】B C C A
Must 提问的肯定回答用must,否定回答不能用Mustn’t，而要用Don’t have to或needn’t
--Must he come to sign this paper himself?
--Yes, he ____.
A need B must C may D will
【答案】B
五 表示祝愿
Wish you all the best! 祝万事如意。
May you succeed! 祝你马到功成！
May you two live happily ever after! 希望你们两人幸福美满！
六 情态动词分组对比
shall, should ，ought to
1、情态动词中有三个词表示强烈的语气，一个是前面说的must,一个就是这里说的shall（第三个是should,在后文中会提到）。
It has been announced that candidates _______ remain in their seats until all the papers has been collected. (2002上海)
A can B will C may D shall
【答案】D
2、should 表示劝告，建议 = ought to 应该
According to the air traffic rules, you ________ switch off your mobile phone before boarding. (2008上海)
A may B can C would D should
Oh, I’m not feeling well in the stomach. I _____ so much fried chicken just now. (2002上海春)
A shouldn’t eat B mustn’t have eaten
C shouldn’t have eaten D mustn’t eat
【答案】D C
3、should还可以表示说话人的感情，如惊奇、愤怒、失望等，表示“竟然”。
You can’t imagine that well-behaved gentleman____ be so rude to a lady.(2001上海)
A migh B need C should D would
【答案】D
Would, used to
表示过去的习惯性动作
Would 只能用来表示重复的动作而不能表示状态,常跟过去的具体时间连用；
Used to 既可表示动作也可表示状态, 而且强调现在已经不这么做了
When he was working in the suburban area, he would go into town for shopping every weekend.
当他在郊区工作的时候，他常常周末到城里购物。
He used to be a nice man. But now he is addicted to alcohol and beats his wife.
他以前是个不错的人。但是现在，他成了个酒鬼，还打老婆。
need ， dare
这两个词，既可以作情态动词，又可以作实意动词。作为情态动词，两者都只能用于疑问句，否定句和条件句。
作实义动词，不能直接加动词原形，要加不定式符号to
She needs to do it.
I dare to do it.
作情态动词，直接加动词原形。
I dare not do it.
I need not do it.
need作情态动词，表示“有必要”，多用于疑问句和否定句
--What sort of house do you want to have? Something big?
--Well, it _____ be big—that’s not important.(2008陕西)
A mustn’t B needn’t C can’t D won’t
As you worked late yesterday, you ______ have come this morning. (2006陕西)
A mayn’t B can’t C mustn’t D needn’t
【答案】B D
need作实义动词，表示“必须，需要”
You need to tell us the truth.你必须讲实话。
The car needs repairing. 车子要修了。
The door needs to be repaired immediately. A thief might break in. 这扇门必须马上修好，否则小偷会进来的。
相关练习：
1 John promised his doctor he ______ not smoke, and he has never smoked ever since. (2008北京)
A might B should C could D would
2 --What’s the name?
--Kuhulaifi. _______ I spell that for you? (2006北京)
A Shall B Would C Can D Might
3 –The woman biologist stayed in Africa studying wild animals for 13 years before she returned.
--Oh, dear! She _______ a lot of difficulties!(2005江苏)
A may go through B might go through
C ought to have gone through D must have gone through
4 The World Wide Web is sometimes jokingly called the World Wide Wait because it _______ be very slow. (2005浙江)
A should B must C will D can
5 –Do you know where David is? I couldn’t find him anywhere.
--Well. He _______ have gone far—his coat’s still here. (2005湖北)
A shouldn’t B mustn’t C can’t D wouldn’t
6 –Could I have a word with you, Mum?
--Oh, dear, if you _____ .(2006浙江)
A can B must C may D should
7 Although this _____ sound like a simple task, great care is needed.(2008四川)
A must B may C shall D should
8 –Excuse me, but I want to use your computer to type a report.
--You ______ have my computer if you don’t take care of it. (2004湖南)
A shan’t B might not C needn’t D shouldn’t
【答案】D A D D
A B B A
参考资料：http://blog.sina.com.cn/s/blog_601f03520100ec6l.html