What is an example of metaphor in "To Build a Fire"?
"To Build a Fire" is written in the Naturalist and Realist styles, where events and prose are detailed realistically. This means that there are not many metaphors; there are no need for them, as the reader is presented with exactly what is on the page, without comment or interpretation. For example, in the introductory paragraph, the omniscient narrator states:
It was a clear day, and yet there seemed an intangible pall over the face of things, a subtle gloom that made the day dark, and that was due to the absence of sun.
This is in contrast to a metaphorical reading of the dark-yet-clear day, which might compare it to, for example, a clear pond which is still opaque in its deeper areas.
One good example, one of the very few that exist in this story, refers to the customary tone that men use to talk to their sled-dogs. Since the dogs are working animals, the men do not speak to it as a pet, but as an employee or slave, and the dog has associated the sounds of human voices with punishment.
His erect position in itself started to drive the webs of suspicion from the dog's mind; and when he spoke peremptorily, with the sound of whip-lashes in his voice, the dog rendered its customary allegiance and came to him.
(London, "To Build a Fire," jacklondons.net)
The man's voice is not literally built of whip-lashes, nor does it sound like one. However, since it symbolizes the sting and sound of the whip to the dog, it is likened to that consequence. The man's voice is one of the things that make him an unsympathetic protagonist; since he doesn't care about the dog, or about anything but the "Real," it is hard to empathize with his situation. When he thinks about killing the dog to use its warmth, the reader sees the ultimate pragmatism of his position; his voice, equated with whips, is not comforting to the dog, and so both the reader and the dog understand that his intent is entirely selfish.