1） be +现在分词,构成进行时态,例如：
They are having a meeting. 他们正在开会.
English is becoming more and more important. 英语现在越来越重要.
2) be + 过去分词,构成被动语态,例如：
The window was broken by Tom.. 窗户是汤姆打碎的.
English is taught throughout the world. 世界各地都教英语.
3） be + 动词不定式,可表示下列内容：
a. 表示最近、未来的计划或安排,例如：
He is to go to New York next week.. 他下周要去纽约.
We are to teach the freshpersons. 我们要教新生.
说明： 这种用法也可以说成是一种将来时态表达法.
b. 表示命令,例如：
You are to explain this. 对此你要做出解释.
He is to come to the office this afternoon. 要他今天下午来办公室.
c. 征求意见,例如：
How am I to answer him? 我该怎样答复他?
Who is to go there? 谁该去那儿呢?
d. 表示相约、商定,例如：
We are to meet at the school gate at seven tomorrow morning. 我们明天早晨7点在校门口集合.
英语的“be”是个特别动词；有些语言,如中文和马来文,并没有“be”这样的动词.
“Be”除了原形的“be”之外,还有另外七种形式：am, is, are, been, being, was, were.
在句子中,“be”可以是主动词(The Principal Verb)或助动词(The Auxiliary Verb).
当主动词时,“be”在性质上属于接系动词(The Linking Verb), 后面要有名词、形容词、地方副词或短语作补足语(The Complement).例如：
1. The man is a science teacher.
2. Mary's new dresses are colourful.
3. I have been there before.
4. Mother is in the kitchen now.
这四个都是陈述句,可以变成疑问句,方法简单,把主语和“be”或助动词对换位置即可：
5. Is the man a science teacher?
6. Are Mary's new dresses colourful?
7. Have I been there before?
8. Is mother in the kitchen now?
当“be”要在祈使句中出现时,它必须借重助动词“do”或“don't”之助,如：
9. Don't be silly!
10. Do be obedient!
11. Don't be a fool!
“Be”有两种缩写法,如下：
12. He's not./He isn't.
13. You're not./You aren't...
但“am + not”的缩写法只有一个：
14. I'm not.
有人用“ain't”, 但这并不是标准英语.
谈过了“be”作主动词的功能,现在看看“be”作助动词时,有些什么用法：
1.“Be + 现在分词”以组成进行式时态(Continuous Tenses),如：
15. Tony's maid is washing his new car.
16. The children are playing in the field.
17. Samuel was eating when I came in.
18. We have been living here since 1959.
2.“Be + 过去分词”以组成被动语态(The Passive Voice),如：
19. Her money in the drawer was stolen.
20. A number of good jobs are taken up byforeigners.
21. David studied in Taiwan but has been trained as a language lecturer in America.
22. Can all the wonderful birds be found in our Bird Park?
23. The disobedient boy was told to stand out- side the classroom.
24. Steps are being taken to reduce traffic con- gestion during peak hours.
25. Dishonest students will be immediately dealt with.
从上面例子看,“be”这动词外貌平凡,但内涵丰厚.如果没有“be”,补足语的桥梁断了.如果没有“be”,何来进行式时态和被动语态?缺了这几样重要的句式,英语还像英语吗?求采纳