The novel uses a string of metaphors to describe the feeling on the hacienda as John Grady breaks the horses in Part 2:
By midmorning eight of the horses stood tied and the other eight were wilder than deer, scattering along the fence and bunching and running in a rising sea of dust as the day warmed, coming to reckon slowly with the remorselessness of this rendering of their fluid and collective selves into that condition of separate and helpless paralysis which seemed to be among them like a creeping plague.
Despite John Grady’s simple, practical language and his insistence that he has the technical skills to break all the horses, these metaphors comparing the cloud of dust to a wild sea and the horses’ taming to paralysis reveal the extreme significance and meaning of this event. John Grady believes he is proving himself as a capable horse-tamer, but he does not have the wisdom to understand that he is not only changing the course of his life, but of all the horses’ as well. These cosmic metaphors suggest that John Grady's time spent on the hacienda will have far greater importance for his development than may seem obvious. The use of metaphor here underscores this idea figuratively, since John Grady has not yet had the experiences he would need to articulate this literally. The metaphors suggest that the young man is still inexperienced and has a lot to learn.
In Alfonsa’s final speech to John Grady in Part 4, she uses a metaphor to insist that Spaniards (and, by extension, Mexicans) mediate reality by cruelty:
In the Spaniard’s heart is a great yearning for freedom, but only his own. A great love of truth and honor in all its forms, but not in its substance. And a deep conviction that nothing can be proven except that it be made to bleed. Virgins, bulls, men. Ultimately God himself.
Blood here is a metaphor for control and violent conquest. This blood, Alfonsa argues, is the basis of the Spanish worldview: “nothing can be proven except that it be made to bleed.” The violence and domination that blood represents, to Alfonsa, makes up the very fabric of reality in Mexico. Everything else, from "virgins" to "bulls," is legitimized through this "bleed[ing]."
Alfonsa takes care to warn John Grady of this reality because (despite his personal encounters with violence) he still believes that love and romance can overcome harsh reality. Because she is much older than John Grady, though, Alfonsa realizes that violence and blood dictate reality—nothing can exist outside of them. Using blood as a metaphor here allows her to discuss the societal proliferation of violence in figurative terms.