一、MIGHT
1.1 表示可能性（Possibility）：
It might rain today.
They might go to the cinema.
They might not go to the cinema.
We might go to dinner tonight, I'm not sure.
It might rain tomorrow.
He might not go to Japan next year.
You might shoot another panther this year.
1.2 其他用法：
You might post this for me.（请求）请你把这信寄一寄。
You might at least apologize. （责备）你至少该赔个不是。
He might at least have offered to help me.（责怪）他至少该说来帮助我。
I might have been a rich man.（懊悔）我该做到富翁了。
二、CAN
2.1 表示有能力：
Sam can play the guitar.
Can Howard sing?
He can't (cannot) understand German.
2.2 表示许可：
Can I park my car here?
No, you can't, it is a no parking zone.
Can I go to the theatre with Zhang?
2.3 表示可能：
A car can be a useful means of transport or a dangerous weapon.
She can be very hard to understand sometimes.
We can live life with a positive or a negative attitude.
2.4 在否定或疑问时，有“何至于”，“不可能”之意：
He cannot be a cruel man. 他不可能是一个冷酷的人。
Can they have said such a thing? 他们何至于说出这样的话？
三、COULD
3.1 作为can 的过去式：
She couldn't (could not) come to dinner last night.
They could walk faster when they were younger.
Sam could play the piano when he was a boy.
3.2 客气请求：
Could you tell me the time, please?
Could you help me, please?
Could I have a coffee, please?
Could we come and visit you this evening?
3.3 could not help-ing, could not but 有“不禁”，“忍不住”之意：
We could not but laugh. 我们忍不住发笑了。
We could not help laughing. 我们不禁笑了起来。
四、MUST
1、表示“必须”：
You must listen to him. 你必须听他的话。
(注意：如果要说“你不必听他的话。”可不能说“You must not liston to him。”而要说：You need not liston to him. 因为“You must not liston to him.”的意思是“你不可听他的话。”）
2、表示“一定”：
He must be a honest man. 他一定是一个诚实的人。
3、表示"偏偏"：
As I was sitting down to supper, the telephone must ring. 当我正在坐下来吃晚餐的时候，电话偏偏响了起来。
4、“must have+(past participle)...”的用法：
4.1 “谅必曾经”的意思：
You must have seen him yesterday. 你谅必曾在昨天看见他。
4.2 “谅必曾经（但实在不曾）”的意思：
You must have seen him if you had been here yesterday. 如果你昨天在这里，必曾经看到他。（实际上是不曾看见。）
4.3 “必须曾经”的意思：
Any applicant for this position must have practised for five years. 对于这个职位的任何申请人必须曾经实习过五年。
在英文里，助动词（Auxiliary Verbs)说多不多，说少也不少。这里所谈的只是其中的
一部份，其他如：have, be (am, is, are, were, been, being), ought, need, dare, used to 等等。下面仅谈其中need和dare。
一、NEED ：当用作助动词时，它的特征是：第三人称、现在式（Present tense)、在
疑问句或否定句里指过去、后面的infinitive没有“to”；
Need he go yesterday?（注意：句子指过去，但need为现在式，he go 不作 he goes）
He need not go yesterday.
He need not have any help from us yesterday.
二、DARE ：和need一样，dare 和 need 除了用作普通的动词外，也可用作助动词。它的句子特征是：否定或有否定意味、dare后面的infinitive没有"to"、用dare不用dares、有时指过去的事：
He dare not go.
He dare not do anything.
He dare not take such a step.
No-one dare go.
Dare he go?
“I dare say”这种说法有“我以为”、“大概”、“在我看来”、“或者”的意思：
I dare say it will be right.
His brother, I dare say, is richer.
I dare say his brother is richer.
