Most Common Grammar Mistakes in English - Is it I or Is it me?

“It is me” or “It is I”?

Wrong: It is me, the great tyrant Tyrannosaurus!
Correct: It is I, the great tyrant Tyrannosaurus!

It is important to note that “is” is a linking verb, meaning it renames the subject with a subject predicate in English grammar. 

Now, normal transitive verbs have an object. (He sees me) Me = object.

Linking verbs have subject predicates instead. (That guy was I) I = subject predicate.

Here’s another example. – “A dog is a great pet.”

A dog = subject
a great pet = subject predicate

You can see that “subject = subject predicate”. A dog = a great pet. That’s why they are called linking verbs; because they link two subjects.

And since linking verbs link to subjects, subject pronouns must be used. So that’s why it is “It is I” and not “It is me”.