Simon, in the Lord of Flies, is probably the most mysterious of the characters in the novel, but the author has made him mysterious deliberately. Though he features in the plot much less than the key characters like Piggy, Ralph and Jack, his role is symbolically very important.
Golding's story is not just about boys stranded on an island. As you probably know it is about man's behaviour towards his fellow beings. The author has tried to parallel our start in the Garden of Eden (Bible) by making his characters very young boys in a situation where they have to almost start life afresh. They have to form a government and have laws and plan to live and survive together. This causes friction between them and particularly they are very wary of anyone who seems different in any way. Just as the people killed Jesus because they did not understand him and saw his 'differentness' as a possible threat to them, so too do the boys kill Simon.
Simon represents the mystical, the God-like, the dreamer, the visionary, the deep thinker. Lots of the things that make us suspicious of that kind of person. He, like Jesus, is also the boys' conscience; his death will always trouble them. Like Jesus he is a kind of martyr; his death benefits the boys in a way because they will never forget.
Run through the novel again and pick out the bits with Simon in them and keep asking yourself how Simon parallels Jesus in the story.
So, Simon helps Golding to illustrate the cruelty of mankind/the boys and particularly their cruelty towards things and people that they do not understasnd
You've probably got the idea that in 'Lord of the Flies' William Golding is trying to show what people are like underneath all the centuries of civilization - what human beings naturally are. The public schoolboys are forced to go 'back to nature' in order to survive. Now nature can be presented as a very positive thing, symbolising healthy, simple lifestyles, free of pollution and other problems caused by humans. Alternatively, it can be presented as the opposite of this, very rough and dangerous without the effects of civilisation that we've grown used to. Which of these do you think is shown in Lord of the Flies? Generally Golding seems to be rather pessimistic about human nature - the boys become very savage in quite a short space of time - and he presents humans as being very close to the savagery of nature. Bear in mind that "Lord of the Flies" means "Beelzebub", or "devil", and you've got some idea as to the significance of nature in this book!
You'll need to have a closer look at particular bits of the novel where different aspects of nature are described in order to develop these general ideas, but this should give you some help in setting you on your way.
Beast: The beast, the Lord of the Flies, is seen as a real object on the island which frightens the boys. Actually the beast is something internal; the Lord of the Flies is in soul and mind of the boys, leading them to the natural chaos of a society with no reasoning adults. Only Simon understands what the real beast is, but is killed when he tries to tell the boys about the Lord of the Flies.
Conch: The conch shell symbolizes the law and order of the old adult world which Piggy tries so desperately to protect. The conch represents all the authority which the boys are so used to obeying. When Jack destroys the conch, anarchy quickly ensues because any hope of strong, central leadership has been abandoned. The island society collapses into chaos.
Facepaint: This is the excuse many of the boys use for living as hunting savages, instead of civilized English citizens. The paint symbolizes the smoke-screen the beast uses to infiltrate the boys’ souls.
Fire/Smoke: The smoke of the signal fire symbolizes the last best hope of the boys being rescued. To Piggy and Ralph, the fire represents the moral influence of their old life in England. When the fire goes out, Ralph loses his bearings, unsure of his next move.
The fire is diatonically opposed to hunting, the activity of anarchy on the island.
Island: Golding purposefully picked an island to be the landing place of the crashed plane because an island is isolated from the rest of society. The boys have no contact with the outside world and must look to themselves to solve the problems of their own micro-society. In this way, the island, which symbolizes isolation, serves as a perfect backdrop for the frailties of human nature which eventually surface.
Glasses: The glasses symbolize the voice of reason and logic among the boys. Piggy defends his glasses even more than the conch. Piggy, who represents the superego of the boys’ (and society’s) collective personality, uses his glasses to find solutions to the boys’ problems. The most important solution the glasses find is the lighting of the fire, the boys’ best chance of being rescued.
The Parachute Man: The dead body flying in the parachute symbolizes the end of adult supervision of the boys on the island. While the parachute man is flapping back and forth on the island, conjuring up a powerful image of its prolonged death, the Beast, or Lord of the Flies, is prospering under its new control over Jack and most of the other boys on the island. So while the law and order of the adult world is waning, childish chaos is growing exponentially. Simon has a special connection with the parachute man. He climbs the mountain, subconsciously, to determine whether the parachute man is still alive. When he finds out that the man is dead and that the Beast is alive, Simon has a nervous breakdown. The moral confrontation which occurs when Simon has the interview with the Lord of the Flies symbolizes man’s inability to conquer the evil anarchy of the devil.