In "The Guitar," Lorca uses the guitar as a metaphor for the innate pain of the human experience. It is "impossible" to silence this music of mourning, which is emphasized by the repetition in the poem. Pain is cyclical, just like the guitar's "weeping," which is only made possible by the "swords" that strum its "heart."
Readers are also reminded of various types of human pain through a series of metaphors found in the second half of the poem. There is pain in longing for the impossible, much as the "hot sands" might long for a "white camellia." There is pain in not having a sense of purpose, which is reflected in the "arrow" that has no "target." There is pain in not having a sense of balance, much as it would feel to have an "evening without morning." There is also pain in crushed expectations, as one would feel when finding a "dead bird" resting upon a branch.
This series of metaphors brings depth to the "wounds" of the human heart; and yet, humans continue to breathe, to strum a new chord every morning. For they, too, are "impossible / to silence" as they persevere through the impossible, though they lack purpose and experience crushed expectations. Though life's songs may be those of "weeping," the human heart opens itself again and again to the strumming of a new song.