I've been searching around for a definitive answer to this problem, and I haven't found one yet.
I'm wondering what case is used for the subject and the predicate when pronouns are used.

for example, which is correct?

It is he / It is him
I am she / I am her
It's I / It's me

I was taught that in Latin, the "to be" verb is used as an "equal sign"- meaning that the nouns on both sides of the verb must match in case. So in English, would both pronouns take the nominative case? It seems to me that the first choice in each pair is correct, but definitely not used in everyday speech...
Should have done some searching at this site. The subject has been covered many times. See:
He or him which is correct?
"I" or "Me" After "Be"
ah... figured it would have been posted before but I couldn't find it