A linking verb is a verb that connects the subject of a sentence to the complement. It is sometimes called a copula or a copular verb. An example is "The sky is blue"
the linking verb in this sentence is "is" because it connects the sky part with blue. Hope I helped! ( the main linking verbs are: be, am,is, are, was, were, has been, are being, might have been, become, seem, appear, feel, grow, look, prove, remain, smell, sound, taste, and turn)