The significance of the masks in the Lord of the Flies is that they allow the boys to transform themselves from school boys to hunters. Even though the transformation happens on a superficial level at first, the masks give the boys confidence to act more fierce, more savage in keeping with their new outward appearance. When Jack first sees himself in the reflection of the water in the coconut shell, he suddenly feels like a different person, "an awesome stranger" (63).
Jack realizes that wearing the mask and hiding his true appearance frees himself from old expectations. If he looks like that "awesome stranger," then perhaps he can act like him too; the mask became "a thing on its own, behind which Jack hid, liberated from shame and self-consciousness" (64). Jack, and the other hunters as well, are able to shed their inhibitions wearing the masks, which empower them to commit acts that they would not have been capable of as simple English school boys.