The 'BE' verb can be a bit tricky.
- It helps form tenses.
He is running.
We were sleeping.
- It completes a sentence that do not have action verbs.
The tall man[fragment, incomplete sentence]
The man is tall. [complete sentence]
It does not take DO/DOES/DID in questions or negatives sentences.
Is he angry? vs Did he yell?
He is not angry. vs He did not yell.
In Present Tenses
I am I am not He She is She is not (isn't) It We You are You are not (aren't) They
In Past Tenses
I was I was not (wasn't) He She was She was not (wasn't) It We You were We were not (weren't) They