"Closer" has been described as industrial rock, techno, and alternative rock. "Closer" uses elements of funk, avant-garde, and electronic music. The drum track of "Closer" features a heavily modified bass drum sample from the Iggy Pop song "Nightclubbing" from his album The Idiot. The bass drum in "Nightclubbing" was from a Roland drum machine. The samples were produced using two Akai S1100 samplers, each with an expander (essentially four samplers). The samples were then combined with beats produced by a Roland R-70 drum machine. The production features sound effects such as a bass squelch, synth echo, and feedback growl.
Radio edits of "Closer" were created by muting the vocal track for the duration of each deleted obscenity.
Lyrically, "Closer" is a song about self-hatred and obsession, but to Reznor's dismay, the song was widely misinterpreted as a lust anthem due to its chorus, which included the line "I wanna fuck you like an animal". In 2003, VH1 ranked the song at No. 93 in its countdown of the "100 Greatest Songs of the Past 25 Years." The song was ranked at the number-two position on AOL's "69 Sexiest Songs of All Time," mostly due to the explicit frankness of the chorus. "Come on dude: 'I wanna fuck you like an animal'?" remarked Mötley Crüe drummer and The Downward Spiral contributor Tommy Lee. "That's the all-time fuck song. Those are pure fuck beats – Trent Reznor knew what he was doing. You can fuck to it, you can dance to it and you can break shit to it."
In July 2009, the song was voted in at No. 62 on Triple J's Hottest 100 of all time, and in 2010 it was No. 42 on Pitchfork Media's Top 200 Tracks of the 90s.