Simile
A simile is a comparison of one thing to another. It's more explicit than a metaphor, often using the phrase "like a", or occasionally "as if". They tend to be employed in narrative fiction.
In addition to clarifying something using a point of comparison, the specific choice of comparison should match — indeed, it is an opportunity to further establish — the tone and mood of the story. It should be appropriate to both the setting and style, revealing what the narrator, often speaking as a point-of-view character, seemingly most easily calls to mind as an appropriate point of reference.
For example, Neuromancer is about high-tech low-lives. Its poetic narrator describes the dark sky by comparing it to a CRT TV set tuned to a dead channel, that's attempting to show a plain black image but still faintly glowing. At the time, this was a comparison befitting of a cutting-edge, stylised cyberpunk novel.
In steep contrast, Equal Rites is about witches and wizards in a fantasy setting. Naturally, the points of comparison are timeless affairs such as ravens. As with the rest of the Discworld series, it's rather whimsical, with a befitting narrator. Delightfully fanciful comparisons are therefore in order, such as comparing someone's dress sense to that of a very respectable raven.
Snow Crash, another cyberpunk staple, is outlandishly hyperbolic, bordering on outright parody, and so is its similes.
I recommend littering first drafts with, at most, placeholders such as "like a [simile]", so that you can maintain your momentum. When working on a later draft, you can take your time crafting the actual similes.
Examples
The ships hung in the sky in much the same way that bricks don't.
— The narrator, The Hitchhiker's Guide to the Galaxy, 1979
The sky above the port was the colour of television, tuned to a dead channel.
— The narrator, Neuromancer, 1984
Unlike Granny, who dressed like a very respectable raven, Hilta Goatfounder was all lace and shawls and colours and earrings and so many bangles that a mere movement of her arms sounded like a percussion section falling off a cliff.
— The narrator, Equal Rites, 1987
His uniform is black as activated charcoal, filtering the very light out of the air. A bullet will bounce off its arachnofiber weave like a wren hitting a patio door, but excess perspiration wafts through it like a breeze through a freshly napalmed forest.
— The narrator, Snow Crash, 1992
Writing fiction: Simile
