There are four main categories of verbs:
1. action - These are the ones you already know about. He ran down the hall.
2. forms of "to be" (or "state of being" or just "be" verbs) -
"Be" verbs describe the condition of something or someone:
is, am, are, were, was, be, being, been
"Be" verbs are followed by adjectives (words that modify or describe nouns).
He is hungry.
3. Helping verbs look like "be" verbs, but they are helping another (main) verb:
He is running down the hall.
4. Linking verbs connect the two parts of the sentence, but don't show action.
("Be" verbs are a type of linking verb.)
"Linking verbs are verbs that serve as a connection between a subject and further information about that subject. They do not show any action; rather, they “link” the subject with the rest of the sentence. The verb to be is the most common linking verb, but there are many others, including all the sense verbs."
She is a nurse.
The moon is in outer space.
I have become weary of your methodical approach to waltzing.
My teacher seems like a nice person.
Read more at Grammarly.com.
Subject / Verb Agreement