定义 / 说明
情态动词能简洁灵活地表达许可、规则、义务和建议。B1 阶段最重要的是 can/may、must/have to、should。这些形式看起来相近，但语气强度和来源并不相同：有的表示许可，有的表示强制义务，有的只是建议。掌握差异能让你在日常和正式语境中表达更准确。
关键规则
- 日常许可常用 can：You can leave early.
- 更正式许可常用 may：May I ask a question?
- must 表示强义务，常来自说话者立场。
- have to 表示外部规则/情境带来的义务。
- should 表示建议，不是强制。
- 情态动词后用动词原形：must wear, can go, should speak。
例句
- You must wear a helmet here. - 这里必须戴头盔。
- Students have to arrive on time. - 学生必须准时到。
- You can leave early today. - 今天你可以早点走。
- May I use your phone for a moment? - 我可以借用一下你的手机吗？
- You should check the details again. - 你应该再核对一下细节。
常见错误
- ❌ You must to wear a helmet. -> ✅ You must wear a helmet.
- ❌ I can to leave now? -> ✅ Can I leave now?
- ❌ We should to call him. -> ✅ We should call him.