助动词be、have和do
1. Be动词的用法
(1) 助动词be和现在分词一起构成进行时或完成进行时。如：
He is reading. 他在读书。
I'll be waiting for you there then. 我到时在那儿等你。
(2) 助动词be和过去分词一起构成被动语态。如：
Is he taken good care of? 他被照顾得好吗？
They shall be punished. 他们一定要受惩罚的。
(3) 助动词be用作系动词。如：
Matthew is a teacher. 马修是个老师。
We were late today. 我们今天迟到了。
(4) 助动词be和不定式连用，可以表示下面几种情况。
表计划，只用于肯定句和疑问句。如：
We are to discuss it the following week.
我们打算下周讨论那件事。
When is the wedding to be? 婚礼什么时候举行？
表命令，只用于肯定句和否定句。如：
All junior officers are to report to the colonel at once.
全体下级军官都必须立即向上校报到。
Tom says I am to leave you alone. 汤姆要我不理会你。
表可能，多用于被动结构。如：
Her father was often to be seen in the bar of this hotel.
在这家旅馆的酒吧经常可见到她父亲。
Where is he to be found? 在哪儿可找到他？
表示“必须”，“应该”多用于现在式。如：
Nobody is to leave this room. 谁也不许离开这个房间。
What am I to do next？下一步我该做什么？
He's to blame. 该怪他。
表注定，多用于过去式。如：
He was to be my teacher and friend for many years to come.
在 后来许多年里，他是我的老师和朋友。
The professor did not know at the time that he was never to see his native place again.
当时教授不知道他再也见不到他的故土了。
(5) 助动词be用于条件从句。如：
If we are to succeed, we must redouble our efforts.
我们要想成功，必须加倍努力才行。（are to意为“想要”）
(6) be 后接 going to, about to, on the point of 等表示将来时间或根据计划、意图等将要发生的事。如：
It's going to rain. 快要下雨了。(将来时间)
He's about to leave. 他正要走。(将来时间)
2. Have的用法
(1) 助动词have与过去分词一起构成各种完成时态。如：
I have read the book. 我读过这本书。
Kenny has left. 肯尼已经走了。
(2) 助动词have与been+现在分词构成各种完成进行时态。如：
I have been washing the clothes the whole morning.
整个上午我都在洗衣服。
Lambert has been working as a worker here for nearly five years.
兰伯特一直在这里当工人，几乎有五年了。
(3) 助动词have构成had better, had best, had rather等词组。
Had better 和 had best 是“最好还是……”或“还是……好”的意思。在 had better 中，had 不表示过去时间，不能用 have 或 has 代替。had better 后可接不带 to 的不定式或接进行式、完成式或被动语态。had better 的否定式是 had better not。如：
You had better stay at home．你最好呆在家里。
You'd better have had that experience before.
假如你以前有过那个经验就好了。
You'd better not run the risk. 你最好不要冒那个险。
(4) 补充
Have还可用作使役动词和实义动词(表示”有”,”吃”等意义)。如：
They have had the problem solved.
他们让其他人解决了这个问题.(使役动词)
Bad news has wings. 丑事传千里. (实义动词)
What shall we have for lunch? 我们午饭吃甚么? (实义动词)
3. Do的用法
(1) 助动词do, does和did用于构成否定句、疑问句和倒装句。如：
Do you understand all this? 你明白这一切吗？
Don't go yet. 先别走。
(2) 助动词do, does和did用于代替句中的主要动词，以避免重复。如：
He didn't go to the party. Neither did I. 他没有去参加晚会，我也没有去。
I do not agree. Nor does he. 我不同意，他也不同意。
(3) 用于加强语气， do， does和did位于陈述句的动词原形前， do位于祈使句中的动词原形前。如：
Do have another cup of coffee before you go.
走前请一定再喝一杯咖啡。
That's exactly what he did say. 他就是那样说的。
But I do want to go. 可是我确实想去。
(4) 在一些以否定副词如never, rarely, scarcely, only等为首的句子中，如果实义动词是现在时或过去时，助动词do和did可以构成主谓倒装。如：
Never did I tell him about that. 我从来没有告诉过他那件事。
Rarely does it snow in the South. 南方很少下雪。