情态动词用法全解：特点、can 与 be able to 的时态分工、请求语气、must 与 have to 的主客观之分、need 的情态/实义双重用法。
表示说话人的情感、态度和看法。
一、情态动词的特点
- 不能单独使用，后接动词原形。
- 没有人称和数的变化。
- 否定直接在单词后边加 not。
二、can 与 be able to
| 时态 | can | be able to |
|---|
| 现在 | can | am / is / are able to do |
| 将来 | can | will be able to do |
| 过去 | could（区别：过去能够） | was / were able to do（区别：某次通过努力成功做） |
三、may / might、can / could、will / would、shall
| 情态动词 | 常用人称 | 易错点 |
|---|
| may / might | I | *1：肯否不一。疑问：May / Might / Can / Could I borrow your car? 肯定：Yes, you may / can. 否定：No, you may not / can’t / mustn’t. |
| can / could | you, I | *1：肯否不一（同上）。 |
| will / would | you | *2：could, would 表委婉语气，不是过去时。 |
| shall | I, we | *3：shall 用于第一人称，表征求对方意见；will 用于第二人称，表示请求。
e.g. Shall we order some coffee?
e.g. Will you marry me? |
四、had better / would rather / should / ought to
| 肯定 | 意义 | 否定 | 意义 |
|---|
| had better do | 最好做 | had better not do | 最好不做 |
| would rather do | 宁愿做 | would rather not do | 宁愿不做 |
| should do | 应该做 | should not do | 不应该做 |
| ought to do | 应该做 | ought not to do | 不应该做 |
五、must（主观必须）与 have to（客观不得不）
| 句型 | 例句 |
|---|
| 疑问 | Must I finish the task before dinner? |
| 肯定回答 | Yes, you must. |
| 否定回答 | No, you needn't / don't have to. |
| 肯定 | 特点 | 意义 | 否定 | 意义 |
|---|
| must do | 情态动词 | 必须做（强调主观） | must not do | 不许做 |
| must do | 情态动词 | 必须做（强调主观） | need not do | 不必做 |
| have to do | 非情态动词 | 不得不做（强调客观） | don't have to do | 不必做 |
六、need（情态动词 / 实义动词）
| 用法 | 情态动词 | 实义动词 |
|---|
| 肯定 | — | need sth. / to do sth. |
| 否定 | need not / needn’t do | don't / doesn't / didn't need to do sth. / sth. |
| 疑问 | Need ... do? | Do / Does / Did … need sth. / to do sth.? |
七、情态动词与实义动词的疑问、否定结构
- 情态动词：无三单变化，后加 do，否定直接 + not。
- 实义动词：有三单变化，后接 to do，也可加名词，否定要用助动词。
本文由 Word 资料《六年级英语情态动词用法全解（一）》整理发布，供六年级上学期英语语法复习使用。例句与口诀均按原文收录。
