框架结构图
情态动词的核心考点
1.can/could和be able to的用法
(1)can和be able to都表示能力，意思上没多大区别。但can只有现在和过去时，而be able to则有更多的形式。但当成功地完成某一具体动作时，通常不用could而用was/were able to来表示。这时was/were able to 相当于managed to，表示经过一番努力，终于能够完成某事。
Her mother can speak French.
The wounded man was still able to get to the village and was saved by the villagers in the end.
(2)can/could表示猜测“可能”，一般用于疑问句和否定句。
—Can the news be true?
—It can’t be true.
Someone is knocking at the door.Who could it be?
(3)can可以表示理论上的可能性，指常有的行为或情形，意为“有时会……”。
Anybody can make mistakes.
(4)表示请求、允许(表请求时，口语中常用could代替can使语气更委婉，回答时用can)。
Can I go now?
—Could I come to see you tomorrow?
—Yes，you can.(否定答语可用No，I’m afraid not.)
(5)表示惊异、怀疑、不相信的态度(主要用于否定句、疑问句或感叹句中)。
How can that be true？I can’t believe my eyes and ears.
How could you be so careless?
(6)can的特殊用法。
can but只好；can’t but不得不；can’t...too再……也不为过，越……越好
I can but wait.
I can’t but wait.
You can’t be too patient to the customers.
2.may和might的用法
(1)表示允许、请求，might比may的语气更委婉一些。
—May I watch TV now?
—Yes，you may.(Yes，please.)
—No，you mustn’t.(No，you’d better not.)
(2)表示可能性时，might比may的可能性小，may表示的可能性比can小(主要用于陈述句、肯定或否定句，疑问句用can代替)。
The story may not be true.
(3)表示祝愿(不用might)
May you succeed!
(4)may/might as well最好还是……，不妨
You might as well do it now.
(5)may/might well很可能
He may well be late for class.
