The subject of a sentence is the person or thing that is doing the action. Sometimes, the person doing the action is yourself. In that case, you use the pronoun I.
I am playing on a volleyball team.
I will walk to your house after dinner.
I bought a new car last week.
In each sentence, the pronoun I is the subject.
Sometimes, the pronoun I is joined with another noun to make a compound subject. Look at these examples:
John and I are playing on a volleyball team.
Mary and I will walk to your house after dinner.
My husband and I bought a new car last week.
The pronoun I is used in the subject part of a sentence. We sometimes add another person to the pronoun I as the subject of a sentence.
▶Now you try it. Find the subject of this sentence. Jim and I watched a movie last night. Did you figure out the compound subject in this sentence? Good for you.