Through the latter half of The Sun Also Rises, bullfighting becomes a potent metaphor for virility and the worth of men. This comparison is made even more explicit during one of Mike’s drunken rants about Robert, in Chapter 13:
"Is Robert Cohn going to follow Brett around like a steer all the time?"
"Shut up, Michael, try to show a little breeding."
"Breeding be damned. Who has any breeding, anyway, except the bulls? Aren't the bulls lovely? Don't you like them, Bill? Why don't you say something, Robert? Don't sit there looking like a bloody funeral. What if Brett did sleep with you? She's slept with lots of better people than you."
After Mike’s initial comment that Robert behaves like a steer, Brett inadvertently adds fuel to the fire by asking Mike to “show a little breeding,” or behave like the well-heeled member of British society that he is (or was, prior to his bankruptcy). Mike counters with the assertion that the only ones showing any breeding in Pamplona are the bulls themselves, a reference to the careful breeding and selection process that decides which bulls will be used in the festival’s bullfights. This sets up a metaphor distinguishing Robert from Mike because of their different breeding: Mike is a product of “good” breeding, like the kind that would produce a bull. Robert, on the other hand, is Jewish, which—according to someone like Mike—makes him a product of “bad” breeding, like a steer. While steers are ultimately incapable of breeding, bulls are—in their musculature, aggression, and violence—the very image of virile masculine sexuality. In this way, the novel uses the very idea of bull breeding as a metaphor for the ways in which society prizes certain backgrounds while diminishing and discounting others.