Perhaps the most important metaphor in the book, Jake's impotence denies him the relationship with Brett that he desires and seems to shut him off from the possibility of happiness. He is scarred by the war, and the common avenue to happiness is denied him. This wound is a metaphor for the psychic wound that the horror of World War I caused in the culture as a whole.
Jake and Bill fish as a way to connect with and obtain value from the natural world. This common endeavor makes them feel peaceful, calm, and happy. It represents a simple, old-fashioned practice that retains value because it is founded on sound principles.
The consumption of alcoholic beverages becomes an essential part of social interaction in this novel, and characters who do not drink (as Cohn doesn't for most of the time) or who do not handle their liquor well (as Cohn also doesn't the one time that he tries) are rendered socially awkward by this inability to consume. The novel presents an array of beverages and means of consuming them, from wine drunk from a leather bag with Spanish peasants on a bus as a show of congeniality, to beer, absinthe, and a liqueur distilled from the flowers of the Pyrenees. As a metaphor, imbibing liquor could be said to signify a way of coping with the difficulties of reality. Only Bill seems to be a really convivial drinker; he quickly sympathizes with Jake's frustration and impotence, Mike's bankruptcy and troubles with Brett, and Cohn's social challenges.
Boxing appears in the novel through Cohn, and through Bill's tour of Vienna and Budapest. Through Bill, it is a way of creating a spectacle of battle, and it can easily be manipulated or otherwise go wrong. In Cohn, it becomes an arbitrary measure of physical skill with no enduring value or meaning. It does not matter, really, that Cohn can beat Romero at boxing. Romero is far superior in every other way. Perhaps only Edna, after watching Cohn make quick work of Mike and Jake, and Bill, in traveling around Europe to watch boxing matches, show any respect for boxing in itself.
The bullfight becomes one of the last sources of meaning and value in a distorted and damaged world. Though the fights have been threatened by the decadence of some contemporary bullfighters, they remain a place where many people (those with aficion) can see and appreciate real courage and skill, and where greatness cannot be faked. The great bullfighter must have respect for the bull, and respect for the sport, and these things are too strong to be shaken by the war.