Linking Verbs, in contrast, do not show action, but link parts of sentences together. The most common linking verbs are verbs that are forms of to be, such as is, are, and was. The general rule is that if the verb in a sentence can be replaced by a form of to be, the verb is a linking verb. The sentences, “Maria Mitchell became a famous American astronomer” and “Maria Mitchell was a famous American astronomer” express similar ideas and make sense.