In introducing Queen Gawaine in Chapter 1 of The Queen of Air and Darkness, White introduces a black cat and describes it using a compelling and odd simile:
The black cat lay on its side in the firelight as if it were dead. This was because its legs were tied together, like the legs of a roe deer which is to be carried home from the hunt. [...] This cat, with the small flames dancing in its oblique eyes, was perhaps seeing the pageant of its last eight lives, reviewing them with an animal's stoicism, beyond hope or fear.
The simile introduced in the first sentence of this passage is blunt and direct: the cat lay "as if it were dead." The reader assumes this simile is meant untruthfully, that the cat is merely quite lazy or sleepy. White uses the reader's conception of cats against them. We find in the next sentence that the cat in fact truthfully looks like it is dead, its legs tied like a hunted deer. (This is because the Queen wants to use the cat as an ingredient in a "well-known piseog to amuse herself, or at any rate to pass the time while the men were away at war.") Similes can be more or less truthful, to different effects; White plays with that fact here.
Most effective in this simile, though, is that the cat is very much alive even while it looks quite literally dead. "Small flames" still burn in its eyes, as White metaphorically shows the cat's still burning vitality. This later description, which speculates on the cat's reminiscence in its final moments, does not use figurative language like the earlier simile about the cat. Instead, it is direct and straightforward, describing exactly what the cat is doing as it looks back over its "eight lives." White, in this passage, does not only use figurative language to great effect, but modulates how figurative his language is, with deftness.
During one of Lancelot's quests, the narrator uses a simile to describe "two knights on the borders of Wales called Sir Carados and Sir Turquine":
They existed like eagles, to prey on weaker brethren. It is unfair to compare them with eagles, for many of these birds are noble creatures, while Sir Turquine at any rate was not noble.
These sentences, strange and self-contradictory yet elegant and funny, are quintessential White. First, there is a simile to describe the two knights: "they existed like eagles." This, already, is an effective simile for how novel it is; kings are often compared to animals for their fearsome strength or power. But a simile in which these knights are compared to an eagle, and negatively, is a compelling reversal.
But then the narrator undercuts his own simile immediately. He says "it is unfair to compare them with eagles." It is as if in the space of a sentence, the narrator changed his mind. His reason is that eagles are noble, and "Sir Turquine at any rate was not noble." White includes an odd oxymoron in that sentence: "Sir," as a title, should imply that its holder is noble. This is because knights of this time, who then and now have the title "Sir" with their name, had to be born of nobility. But Sir Turquine is not noble—a paradoxical situation. So as a whole, the simile and the narrator's questioning of it forms a subtle but effective comment on Sir Turquine: it is not where you come from but how you act that makes you noble, like an eagle.