What is a controlling metaphor?

A controlling metaphor is one that dominates or controls an entire literary piece. This literary device is frequently seen in poetry. It is similar to an extended metaphor, which extends over a large portion, but not all, of a literary piece.

A metaphor is a term for two dissimilar things being compared implicitly without using like or as. For instance, "the cloud is a bunny." A simile is similar to a metaphor, but it does use like or as. For instance, "love is like a rose." Mixed metaphors are formed when two metaphors that are incompatible are combined and become unclear and sometimes humorous, although the humor may be unintentional.