Subject in English

The subject is the agent on the sentence in active voice, it is the person or thing that performs or is responsible for the action of the sentence. 
NOTE: Every sentence in English must have a subject.


Coffee is delicious and Milk contains calcium.


The subject may be  noun phrase. 


The Book is on the table.
That new red car is John's


Look at this example of subject: 


We Girl's are not going to that movie
George likes boats
Mary and I went to a restaurant last night
The Weather was very bad yesterday




It can act as a pronoun or can be the subject of an impersonal verb. As the subject of an impersonal verb, the pronoun is not actually used in place of a noun, but is part of an idiomatic expression. 


It rains quite often here in the summer
It is hard to believe that he is dead


In some sentences, the true subject does not appear in normal subject position. However, the true subject appears after the verb.


There was a fire in that building last month
Was there a fire in that building last month?


There were many students in the room
Were there many students in the room?


Okay, keep studying friends 
Spirit!