I find that many authors write weak similes and metaphors. Part of the reason for this is that they don't understand the purposes of figurative language. Similes and metaphors can serve several different purposes, such as creating atmosphere and introducing symbolism, but the main purpose of these techniques is to help describe something that's difficult to describe. The author thinks, "Okay, I can't really describe X, so instead I'll compare it to Y, with which readers are very familiar, so they can see X more easily." That can work very well. But many times writers compare an X to a Y that we aren't familiar with, so X is not illuminated by the comparison. This strange Y is distracting or confusing, rather than helpful. Other problems are that Y may not be a true parallel to X, or that an author compares X to several different things, and those things create contradictory images.
For example, "Simon leapt to his feet like a man who had just emerged from a time warp."
I have no idea how a man who has just emerged from a time warp would jump to his feet, so this doesn't help me picture the way Dexter leapt to his feet. Instead, I'm distracted by the idea of time warps, and a man emerging from them, which has nothing to do with this story.
Another example: "'Come in,' I heard a voice muse through the flame, a voice that sounded like an army of ghostly voices all speaking as one from miles and miles above."
Above, the author is comparing the voice to an army of ghostly voices miles and miles above. I have no idea what ghosts sound like, let alone ghosts miles and miles above me, so this comparison doesn't help me hear the voice any more clearly. I end up imagining some corny, clichéd ghost voice from some bad horror movie. That's not good.
A metaphor example: "And I drove my hand into her chest, into a warm, fleshy glove, felt the ribs scrape over my palm, felt the beating of the Heart."
I like the fleshy glove comparison very much; I know what a glove feels like, and that allows me to feel a very gross sensation. But the scraping of the ribs contradicts the fleshy glove image. The author needs to keep the imagery consistent.
- They were spinning outward like a never-ending spiral of chaos that wrenched every single atom of John's being away from his core and into the swirling realities.
- I felt like I was ripped into a thousand tiny pieces and thrown into a tornado.
- The truth hurts. Maybe not as much as jumping on a bicycle with the seat missing, but it hurts.
- She marched down the street like any veteran soldier rolling up the last mile between her and her bed.
Good similes and metaphors are very difficult to write. Just keep trying!