BBC Verb to be, present and past
The form of the verb to be is am (contracted to 'm), is ('s) and are ('re) in the present tense and was/were in the past. To beis used as an auxiliary verb, to form continuous tenses and the passive, and as a main verb. Here we are looking at it as a main verb.
After the verb to be we use an adjective phrase, a noun phrase, a preposition phrase or an adverb phrase.