You may have heard “it is me” many times, especially by Americans and native English speakers. It is wrong. Why?
“Me” is an indirect object pronoun, as in “Mrs. Merkel gave the hat to me”. Mrs. Merkel is the subject, “gave” is the verb, “hat” is the direct object (of the verb) and “me” is the indirect object.
So, when someone asks “who is it?”, the correct answer is “it is I”. The grammar rule – it is the same in Spanish – is that the verb “to be” has no object. Would you say in Spanish: “me” o “es me”? No. So why do it in English?
So, why do many people make such a big mistake?. The answer is probably unthinking minds (mentes irreflexivas).
