The rain is a metaphor for death in the story. Toward the end of Catherine and Frederic's idyll in Milan, she tells him that she has always been afraid of the rain because she can imagine herself or him lying dead in it. He replies that he has always liked the rain and through this comment we understand that though he has suffered a combat injury and seen men die, he has not been touched by fears of mortality. Catherine on the other hand has been deeply affected by her fiance's death. For her, death is a more immediate and palpable and the rain serves to remind her of her mortality and the mortality of those she loves. Thus the rain falls when death is most tangible, such as when they part at the train or when Frederic narrowly escapes being shot by diving into the river. Most significantly, when Frederic leaves the hospital after Catherine has died, we are told that he walks back to the hotel in the rain. He is familiar with the emotional ramifications of death and its ability, like the rain, to fall upon anyone at anytime.
The characters of Rinaldi and the priest
Hemingway's lean prose style coupled with Frederic Henry's matter-of-fact narration does not yield many metaphors in A Farewell to Arms, but in a sense Rinaldi and the priest come to represent two aspects of Frederic's character. Rinaldi's boisterous and passionate personality is in tune with Frederic's character when we first meet him as a young man with no personal attachments and a debaucherous disposition. When he returns from his first leave and describes the worldly pleasures of Milan, Rinaldi shares in his friend's delight as it reaffirms the drinking and whoring they have enjoyed together before. The priest, during this time, is cowed by the officers at the mess and is timid in his friendship with Frederic. After Frederic has fallen in love with Catherine and experienced a true love, it is the priest with whom he identifies and finds an outlet for his more serious musings. Significantly, Rinaldi is suffering during this time. He blunders in making light of Frederic's feelings for Catherine. He has become cynical and morose. He makes a drunken scene at the mess and fears he has contracted syphilis. He is jealous of Frederic's love and he privately confesses that his only pleasures remain in his work and in drinking and whoring, neither of which appear to have the power to sustain him.
Sports, Competition and Love
Thoughout the story, Hemingway uses sports and gaming metaphors to reflect on the quality of love. Frederic's initial attraction to Catherine is tied to winning her affection as in "the moves in a chess game". Later, he compares their relationship to a game of bridge where "nobody had mentioned what the stakes were. It was all right with me." In this way Catherine, unlike the girls in the bordello, presents a challenge and something to be prized. The sports metaphor is used again during the group trip to the horse races. When Catherine and Frederic bet with the group they win, but they discover that they are happiest by themselves. Even though the horse they choose comes in next-to-last, it doesn't spoil their mood. This episode reflects a deeper understanding of love in which competition has been replaced by understanding and support.