A subject is the person or thing that a sentence is about. A subject does the action in a sentence.
I collected colorful fall leaves for an art project.
I have been studying math all weekend.
In each of these sentences, the pronoun I is the subject of the sentence.
When we use the pronoun I, we are talking about ourselves and what we are doing.
Look at these sentences. Each has a pronoun mistake that writers often make:
Me and my class collected fall leaves for an art project.
Me and Emma have been studying math all weekend.
For some reason, when we add in another person along with us, we forget to use the pronoun I.
We would never say Me collected fall leaves – so we should also never say Me and my class collected fall leaves.
The correct sentences look like this:
My class and I collected fall leaves for an art project.
Emma and I have been studying math all weekend.
Always use the pronoun I as a subject who is doing something. When you are doing something along with somebody else, always put the other person first.