I’ve written about [tag]linking verbs[/tag] before but never named the complement that completes a linking verb sentence. This would be the famousÂ [tag]predicate nominative[/tag].
Let me give you an example: "I am Gary." The verb am is a form of the verb to be, which shows a state of being and therefore cannot take an object, so it must take a predicate nominative, which is Gary in this case.
Another example: "His favorite book is Exodus." Can you name the subject, verb and predicate nominative in here? Book is the subject, is the verb, and Exodus the prdicate nominative.
Remember linking verbs show state of being, as in these examples, or simply link the subject with a modifier, as in, "This soup tastes good." Soup is the noun, tastes the linking verb, and good the modifier.
In these examples, the nouns (Gary and Exodus) and adjective (good) are functioning as a nominative (subject) following a verb (predicate), thus the name predicate nominative. In a way, then, there are two subjects in each of these examples, which are joined by linking verbs.