Movement
The comparison inherent in the simile is an excellent tool for efficiently describing movement that might otherwise be difficult to portray. In science fiction, especially, similes are a powerful tool:
“But when she moved that way, twisting, hurling herself into controlled falls, landing running, she seemed not only boneless, but aquatic—something swimming through the air as though it were water.”
Emotions
The simile is also effective for conveying emotions; or the lack of an ability to control them.
“How much more time and energy are you going to waste resenting her?”
“As little as possible,” I said. “I can’t quite turn it off like a water faucet though.”
Dialogue
Some people speak in metaphors all the time. Others are much less robust with their figurative imagery. Either extreme can make the use of a metaphorical image more powerful, but what is important to remember is that dialogue and conversation can be a shortcut for characters to intensely express themselves in a way that gets right to the core of the matter:
“I won’t be a puppet. I won’t be controlled”
Animals
The use of an animal to make a comparison is often exploited for the purpose of simile. By contrasting human behavior with animal behavior, the deviance from the norm can be easily heightened:
“Today’s children gathered books as well as wood to be burned as fuel. They ran through the streets chasing one another and hooting like chimpanzees. They had no future. They were now all they would ever be.”
Obsession and Archery
Metaphorical imagery can also be especially obliging for the purpose of comparing two things that appear to be completely unrelated to each other in any way. Like, for instance, obsessiveness and shooting arrows at a target:
“I saw positive obsession as a way of aiming yourself, your life, at your chosen target. Decide what you want. Aim high. Go for it.”