Rat Kiley is the prototypical storyteller, always relating something that happened somewhere else. He teaches "O'Brien" the power of the story. Even an unreliable storyteller, as Rat is, can still command the attention and belief of his audience because people like hearing his stories. Rat is well regarded, even though people knew him to exaggerate. He is integral to the life of Alpha Company — the medic who helps the others out. When O'Brien was shot the first time, Rat helped him, saved him. He is a combination of teller and doer, the man who could tell a story as well as patch a wound.
Rat also teaches us the limits of what a man can take. Rat shoots himself in the foot as a result of the company switching to a routine of night-movement for two weeks. As night is a common metaphor for death, we understand how Rat deals with the new, pressing presence of death around him. Rat's paranoia, his visions of body parts, is his fear manifesting itself, and because he is such an enthralling storyteller, he makes the others in the company (as well as the readers) feel his fear too. Where Bowker commits suicide and Mary Anne Bell becomes an agent of the wild, Kiley decides to remove himself from death by shooting himself in the foot. All of these characters demonstrate how each person deals differently with the limits of innocence and human understanding when confronted by something as powerful and terrifying as war.