Simon is typically seen as a Christ figure in "Lord of the Flies." This is because he bears resemblance to Christ in the following ways: he is good with children (he is often described as picking fruit for the littl'uns), he is a prophet (he tells Ralph that Ralph will definitely make it off the island), he spends some time alone in the wilderness (his "clearing") and, while there, he struggles with the "devil," represented by the Lord of the Flies, or Beelzebub - the Greek word for devil. Also, he discovers that the essential illness of mankind is our own inherent evil and when he tries to spread this message, he is killed by his peers.
Authors often use Christ figures to make some kind of commentary on religion or faith. By having the boys not hear Simon's message, but instead brutally murdering him, Golding could be suggesting that part of their inner savagery coming out includes a loss of faith, or at the very least, a denial of human's essential illness.