Human beings, you see, do absolutely two primary things. We see like and unlike. Like becomes, in literature, simile and metaphor. Unlike becomes uniqueness and difference, from which I believe, the novel is born.
A simile is just a metaphor with the scaffolding still up.
I can never look now at the Milky Way without wondering from which of those banked clouds of stars the emissaries are coming. If you will pardon so commonplace a simile, we have set off the fire alarm and have nothing to do but to wait. I do not think we will have to wait for long.