Linking verbs connect the subject of a sentence to a noun or adjective that renames or describes the subject. Common linking verbs include:
* be (am, is, are, was, were, been, being)
* become
* seem
* appear
* feel
* look
* sound
* taste
* smell
"Had" is a helping verb (also called an auxiliary verb). It is used with a main verb to form a verb phrase.
For example:
* She had gone to the store. (Had + gone = verb phrase)
* They had eaten dinner. (Had + eaten = verb phrase)
In these examples, "had" helps the main verbs "gone" and "eaten" to show past perfect tense.