Fire plays multiple roles in Lord of the Flies.
First, the boys use fire as a signal to attract the attention of passing ships. In the second chapter of the novel, "Fire on the Mountain," the boys haphazardly attempt to make their first fire after Ralph speaks of the importance of rescue. The boys rush off to create a huge and deadly signal fire that ends up raging out of control. After the disaster of their first fire, the boys realize that fire is not to be underestimated.
Fire also becomes vitally important to the boys on the island for cooking after Jack and his hunters kill their first pig. Ultimately, Ralph and Jack will clash over what is more important--maintaining a signal fire or hunting.