Lord, referencing power and authority.
Flies, referencing something that is rotting. It doesn't get much clearer than that.
In this disturbing look at human nature, a bunch of boys between the ages of 6 and 12 (notice that this is before the age of teenage testosterone rages) crash land on an island. The wreckage left "a scar" on the island (symbolism!!). Ralph and Piggy find a conch (more symbolism!!) and call the others to a meeting. Some of them show up wearing all black (symb.... ok, you get it). One kid wants to be made supreme ruler because he can sing a C#, and another one just wants someone to be named chief so that they can organize and get some stuff done (also notice the difference here in supreme ruler vs a leader of peers). The kids vote for the leader of peers and C# boy will never be happy with that.
The conflicts thereafter show the differences in priorities as extensions of each character's personality. Is it more important to make and maintain a signal fire so that they can be rescued? Is it more important to build shelters? Is it more important to maintain a sense of civilization and rules? Or is it more important to go on pig-slaughtering sprees? In a nutshell, will creating win out over destroying if the boys are left to themselves? And if they get rescued, aren't they simply being taken to a grownup world in the middle of their own war that is as bad as the one that will inevitably happen on the island?
Before long, they are all long-haired, dirty, mostly naked, covered in warpaint, participating in ritualistic dances and animal sacrifices, and beginning to target each other. So, there ya go.
Lord of the Flies not only does an excellent job of exploring human nature, but also making us ask questions about the value of civilization, rules, and identity as well as what effects fear and power have on that system. 5 stars from me, and 2 big thumbs down to leaving any more than 2 children to themselves for more than 5 minutes. They will burn down your island.