'Are' is a verb. It is the present tense, plural (all persons) or singular (second person only) form of the verb "to be" in English.
'Are' can be used as a linking verb or an auxiliary verb.
Linking verb: They are happy.
Auxiliary verb: They are running in the marathon.
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "twirl" is a verb.
The part of speech for "explicit" is an adjective.
The part of speech for "indefinite" is an adjective.
The part of speech for "lecturer" is a noun.
The part of speech for "breezy" is an adjective.