Metaphors are comparisons that don't use the words like or as. In chapter 2, the metaphors are simple and commonplace, then grow more vivid as Golding describes the burning spread of the fire the boys build.
Earlier in the chapter, before the fire starts, a little boy steps forward to tell the other boys about the snakelike "beastie" he has seen. Golding uses a very commonplace metaphor when he compares the boy to a shrimp, a small creature, stating:
He was a shrimp of a boy
The metaphors gets a little fresher when the laughter of the other boys hurts the little boy's feelings. In this case, the laughing is likened to being hit, as it is called "the blow of laughter."
Another worn metaphor is applied to Ralph when he is distracted. It is said that "he lost his thread" of his thoughts.
When it comes to describing fire, Golding becomes much more vivid. The fire is compared to a beard as it flames upward into sky:
The yellow flames...poured upwards and shook a great beard of flame twenty feet in the air.
Later, the fire is, as well, likened to a flag: "a clean flag of flame flying."
The fire is also compared to a flaming arm:
The fire thrust out a savage arm of heat.
The fire, in yet another metaphor is likened to an animal chewing away at the forest:
The fire laid hold on the forest and began to gnaw.
When Piggy stares at the fire, it is compared to hell, a place often described as an inferno: "Piggy glanced nervously into hell."
This pile up of metaphors reveals mixed feelings about the fire: it grows from a flag, an item associated with civilization, to being associated with more primal and frightening imagery.
Two lovely and less threatening metaphors describe the sunset. The sun is likened to a drop of burning gold and the world to a window sill:
The sun in the west was a drop of burning gold that slid nearer and nearer the sill of the world.