Mary Ruefle writes:
Metaphor is not, and never has been, a mere literary term. It is an event. A poem must rival a physical experience and metaphor is, simply, an exchange of energy between two things. If you believe that metaphor is an event, and not just a literary term denoting comparison, then you must conclude that a certain philosophy arises: the philosophy that everything in the world is connected. I’ll go slowly here: if metaphor is not idle comparison, but an exchange of energy, an event, then it unites the world by its very premise — that things connect and exchange energy.