What is the primary purpose of a "bridge" in song structure?

The primary purpose of a "bridge" in song structure is to provide a contrast to the verses and chorus. A bridge serves as a musical and lyrical departure from the established themes and motifs present in the other sections of the song. By introducing a different melody, harmony, or rhythm, the bridge adds variety and keeps the listener engaged. This contrast can serve to highlight the return to the chorus or to amplify the emotional impact of the song. It is a crucial element that helps to create a dynamic and interesting listening experience, effectively breaking up the repetitive patterns and enhancing the overall structure of the composition.