Bringing two different things together with an explicit word, such as "like", "just as" or "seems". Unlike the metaphor, the simile makes it plain that they are two things.
In Inferno
See there Farinata, who has risen to his feet: from the waist up you will see him whole. I had already fixed my face on his; and he was rising with his chest and brow, as if he held Hell in great contempt.
Farinata's attitude is described with "as if he held Hell in great contempt". The simile puts into words what the raised body suggests: a man who looks down on punishment from above, as a small thing.
remain recommended to you my Treasure, in which I still live, and I ask no more. Then he turned back, and seemed like those who run in Verona for the green cloth across the field; and he seemed, among them, the one who wins, not the one who loses.
outside they are gilded, so much so that they dazzle; but inside all of lead, and so heavy that those of Frederick, beside them, were of straw.
because sitting on feathers one does not reach fame, nor under a covering; without it, whoever spends his life leaves on earth the trace that smoke has in the air and foam has in the water.
and the severed head held it by the hair, hanging from the hand like a lantern; and it looked at us and said: woe is me! It made of itself a lamp for itself, and they were two in one and one in two; how that can be, he knows who so governs.
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