What similes are used?

Similes are comparisons using like or as. I have included many similes from "A Sound of Thunder." You will want to search the text yourself and see what else you can find. Because Bradbury is a lyrical poetical writer who likes to use vivid imagery, he has included a large number of comparisons in this story to help us imagine what it is like to travel back in time to the age of the dinosaurs.
Some of the early similes in the story attempt to capture the wonder and danger of time travel. Bradbury likens the time machine to:

a gigantic bonfire burning all of Time, all the years and all the parchment calendars, all the hours piled high and set aflame ...

He likens visiting years gone by to salamanders leaping out of a fire. In legend, salamanders were impervious to fire. A time machine makes time itself impervious to being burned up. Now you can revisit it:

Out of chars and ashes, out of dust and coals, like golden salamanders, the old years, the green years, might leap

But the smallest misstep can have giant consequences; Bradbury uses the Grand Canyon to try convey the enormity of the tiniest mistake:

Step on a mouse and you leave your print, like a Grand Canyon, across Eternity.

Once the men are back in time, Bradbury uses similes to describe the dinosaurs:

sounds like flying tents filled the sky, and those were pterodactyls

He uses many similes to convey the enormity and fearsomeness of the T-Rex:

sheathed over in a gleam of pebbled skin like the mail of a terrible warrior.
a fence of teeth like daggers
Its armored flesh glittered like a thousand green coins.

It is so big it can destroy the men easily. It is able:

to twist them in half, to crush them like berries

When it is killed, Bradbury uses more than one simile to describe the enormity of the dinosaur as he falls and dies:

Like a stone idol, like a mountain avalanche
like standing by a wrecked locomotive