动词前面可以加
助动词。
助动词本身无字义，它仅仅是用来帮助主要动词构成各种时态、语态、语气以及否定和疑问结构。
1)由be，have，shall(should)，will(would)构成除现在一般时和过去一般时外的全部时态。如：
I shall be here any minute. 我将随时到达这里。(由shall构成将来一般时)
The train is now rapidly approaching the city of Beijing. 火车现在正迅速临近
北京城。(由is构成
现在进行时)
We shall be having rain, rain, and nothing but rain. 我们会有没完没了的雨。(由shall be构成
将来进行时)
The roads were full of people. We hadn’t foreseen that. 路上都是人。这是我们事先未料到的。(由had构成
过去完成时)
Soon they would have reached their time limit and must return to the camp. 不久规定的时间就要到了，他们就得回营地了。(由would have构成
过去将来完成时)
He has been scoring plenty of goals this season. 在这个(足球)赛季里，他踢进了许多球。(由has been构成
现在完成进行时)
2)由be构成
被动语态。如：
One is not guilty until he is proven. 在没有证明有罪之前，人都是无罪的。(现在一般时的被动式)
She almost felt that she was being mocked. 她几乎感觉到她在被嘲弄。(
过去进行时的被动式)
I suspected that I had been followed and watched since I arrived in London. 我怀疑我到伦敦以后就已被跟踪和监视。(过去完成时的被动式)
I know he hates being interrupted. 我知道他不喜欢别人打断他的话。(
动名词的被动式)
3)由had，should，would，should have，would have等构成各种
虚拟语气。如：
If I had Jim’s build, I’d go out for the wrestling team. 假如我有吉姆那样的体格，我早就去参加摔跤队了。
The soup would’ve been better if it had had less salt. 假如少放点盐，这汤会好喝得多。
4)由do构成现在一般时和过去一般时的疑问结构。如：
When do we meet again? 我们什么时候再见?
Did you know the hot dog did not originate in the United States, but in Germany? 你知道“热狗”不是来源于美国，而是来源于德国吗?
5)由do加上not构成现在一般时和过去一般时的否定结构，也可以构成
祈使句的否定结构。如：
Don’t knit your brow like that. 别那样皱眉头。
We didn’t think we’d be this late. 我们没想到我们会到得这么晚。
当两个或两个以上包含相同助动词的
谓语动词并列时，后面的助动词通常省略。如：
The letter will be typed and sent off immediately. 这封信将立即打好并发出。
Having explained the rule and given a few examples, the teacher asked the students to write some exercises at home. 教师在解释完规则并举出几个例子后，要求学生回家做一些练习。
助动词在句中一般不重读，但当它代替前面的动词或强调动词的意义时则应重读。如：
—Do you speak English? 你会说英语吗?
—Yes, I do. 是，我会说。
But I have done it. 但是我把它干了。