Every metaphor or simile is a little explosion of fiction within the larger fiction of the novel or story.

— James Wood, How Fiction Works

The metaphor is a fabricated image, without deep, true, genuine roots. It is an ephemeral expression. It is, or should be, one that is used only once, in passing. We must be careful, therefore not to give it too much thought; nor should the reader think too much about it.

— Gaston Bachelard, Poetics of Space

“Metaphors matter”, as Bernard Bailyn has reminded us, for “they shape the way we think” — all the more when they make sense in the light of actual experience.

— A. Roger Ekirch

The Difference Between Imagery and Metaphor

A metaphor gives concrete substance to an impression that is difficult to express. Metaphor is related to a psychic being from which it differs. An image, on the contrary, product of absolute imagination, owes its entire being to the imagination.

— Gaston Bachelard, Poetics of Space

And what about the mixed metaphor?

A mixed metaphor is defined as ‘a combination of two or more incompatible metaphors’.

Actually, there is a way in which mixed metaphor is perfectly logical, and not an aberration at all. … In contemporary parlance, what people dislike about mixed metaphor is that it tends to combine two different cliches, as in, say, “out of a sea of despair, he has pulled forth a plum.” The metaphorical aspect is actually dimmed, almost to non-existence, by the presence of two or more mixed cliches (which be definition are themselves dim or dead metaphors).

— James Wood, How Fiction Works

The Secret Of Powerful Metaphor

Often the leap toward the counterintuitive, toward the very opposite of the thing you are seeking to compare, is the secret of powerful metaphor. […] Obviously, whenever you liken x to y, you will be drawing attention to the fact that x is really nothing like y, as well as drawing attention to the effort involved in producing such extravagances. The kind of metaphor I most delight in, however […] estranges and then instantly connects, and n doing the latter so well, hides the former. The result is a tiny shock of surprise, followed by a feeling of inevitability.

— James Wood, How Fiction Works

(I’ve heard that ‘surprise plus feeling of inevitability’ combo before, elsewhere, in describing ‘the perfect ending’ to a story. In short, metaphors and endings have a few things in common.)

Metaphor In Children’s Literature

When the image or metaphor is within a child’s range of sensory, emotional, cognitive and moral experience and is expressed in linguistic terms that can be apprehended and comprehended by young readers, a book becomes classed as a children’s one.

— Maurice Saxby, Give Them Wings