首先一般是跟doing,表現在進行時；

例如：I am jogging.

還可以跟動詞過去分詞表被動;例:The clothes were washed by my mother.

還可以接動詞不定式,表示將來；例：She is to be married with Bob.

My dream is to be a doctor.I think it is quite great to be adoctor.

在句子中，be有兩種主要作用：

一是作為系動詞(The Linking Verb)，本身可以作用謂語動詞；

二是做為助動詞(The Auxiliary Verb)，與謂語動詞一起構成各種時態和被動語態等。
[肯定句] All the wonderful birds can be found in our Bird Park. (助動詞有兩個：can be )
[疑問句] Can all the wonderful birds be found in our Bird Park? (移第一個can)
[否定句] All the wonderful birds can not be found in our Bird Park. (在第一個can 後加not)
[肯定句] I have been there before. (兩個助動詞：have, been )
[疑問句] Have you been there before?
[否定句] I have not been there before.
[肯定句] I shall be having my supper at six tomorrow evening. (兩個助動詞：shall, be )
[疑問句] Will you be having my supper at six tomorrow evening?
[否定句] I shall not be having my supper at six tomorrow evening. 四.助動詞be，無詞義，輔助主要動詞一起在句中作謂語動詞。用法如下：
1. be+doing：構成進行時態，有現在和過去兩種進行時態。

如：
The girls is reading and copying the new words now.
Young Tom was always asking questions and trying out new ideas.
2. be+going to do，表示"打算或將要做某事"，be有現在和過去兩種形式。如：
We are going to plant trees in the park.
I didn’t know if she was going to come here.
3. be+to do，表示"按計劃安排將要做某事"。

如：
The new shop is not to be opened till next Monday. One night an angel came to
Mary and told her that she was to have this special boy.
五.there be
there be句式為：there be+主語部分＋狀語部分，表示"某處存在某物"，be常用現在時，過去時和將來時等。

如：
Oh, cool! And there are many things to see. There is even a deer park in Sanya.
There are about 80 pyramids in Egypt.
Will there be a football match in your school next week?
六，實義be
可以將be視為實義動詞，因為它具有實際的詞義，如"成為;做;發生;舉行;逗留;到達"等。

如：His daughter wants to be a doctor for animals in her twenties.

Kates birthday party
will be at half past six this evening.

Jim has been in China for
morethan two years, but he has not yet been to Yichang