Rain's vocal delivery is polished and expressive, showcasing his growth as a singer. He brings a sense of authenticity to the lyrics, imbuing the song with emotional depth and resonance.

Musically, "Rainism" is a fusion of genres, blending hip-hop, R&B, and pop elements. The song features a catchy, repetitive hook and a driving beat that propels the dance-oriented track forward.

"Rainism" was released in 2004 as the title track from Rain's fourth studio album. The song was a commercial success, topping various music charts in Korea. According to Rain, the song's lyrics were inspired by his own experiences with love and heartbreak.