This is a lesson on the verb "to be" for advanced students or teachers. It covers all the forms of the verb "to be" as main verbs and auxiliary verbs. It also discusses grammatical person, linking verbs, predicate adjectives and nominatives, modal verbs, and finite verbs. It is linked to the following lesson on Grammar Monster:
https://www.grammar-monster.com/irregular_verbs/verb-to-be-in-English.html