The two main characters, Ralph and Jack, argue over the various uses of fire throughout the novel. Golding uses fire as a symbol to represent different features which correlate with Ralph and Jack's separate uses of the element. Ralph believes the fire should be used to signal ships as they are passing the island. When used as a signal, fire symbolizes rescue and civilization. Ralph argues with Jack about the importance of maintaining the signal fire at all times. The signal fire is initially located at the top of the mountain where it would be most visible to passing ships and airplanes. However, Jack convinces Samneric to leave their post, and the signal fire goes out. Eventually, there are not enough boys to maintain the signal fire, and Jack invades Ralph's camp to steal burning logs to start a fire of his own. Jack uses the fire for an entirely different purpose. Jack uses the fire to cook the pigs he hunts, and to smoke out Ralph at the end of the novel. Under Jack's supervision, fire symbolizes destruction. When Jack sets the brush on fire to make Ralph come out of hiding, the entire island goes up in flames.

What is the changing role of fire between Jack's tribe and Ralph's in Lord of the Flies?

Fire, in this novel and many others, is symbolic of life.  Without it, you don't survive, and in LOF they will never be rescued if they don't keep the signal fire burning.  Ironically, it is the entire island on fire (set to "smoke" Ralph out of hiding so Jack's tribe can hunt him down) that rescues Ralph and the others.

Fire brings many comforts--cooked meat, warmth at night, and protection from the beast.  Piggy's glasses are the catalyst to the fire. Whoever has them (symbolic of Piggy's wisdom and ability to "see" clearly what needs to be done), has control of fire, and ultimately power over the other boys.