Run–D.M.C.'s third single, this was the first high-profile rap song to incorporate rock guitar, which boosted its appeal to white listeners the same way "Beat It," with an Eddie Van Halen solo, expanded Michael Jackson's fan base. The guitar part wasn't a sample - it was played by Eddie Martinez, who was a session player most notable for his work with Blondie.
The writing credit on the song went to the three members of Run–D.M.C. (each 19 years old when the album was released), but Martinez got a production credit.
Run–D.M.C.'s DJ, Jam Master Jay, was known to loop riffs from Rock albums for Joseph "Run" Simmons and Darryl "D.M.C." McDaniels to rap over. One of his favorites from the riff from Aerosmith's "Walk This Way," which they recorded in 1986 with Steven Tyler and Joe Perry in the first hit rock/rap collaboration.
The video was the first rap video to air on MTV. Directed by Steve Kahn, it was Run–D.M.C.'s first video. Whodini, Grandmaster Flash & the Furious Five, Kool Moe Dee and a few other rap artists had made videos, but they were low budget productions that MTV wouldn't touch. The clip for "Rock Box" had animation, compositing, and an intro by the comedian Irwin Corey. It also had a guitar, which pleased the MTV programmers.
Thanks to their mentor Russell Simmons (Run's brother), the group made some shrewd business decisions and were savvy enough to make an MTV-worthy video - the group had no interest in making the clip. Since MTV had never played a rap video, the group didn't watch it and didn't think it was a big deal - at the time they were more concerned with getting the clip shown on local shows like New York Hot Tracks. Their label, Profile Records, was much more excited and got a nice return for the $27,000 they spent to make the video.
Larry Smith, who was the group's producer, had the idea for the rock guitar on the song, which the rappers were against, but went along with. They made a version of the song without the guitar, but it was the rocker that caught on. "We didn't want the guitar version playing in the hood," said D.M.C. in I Want My MTV. "But when DJ Red Alert played it on his radio show, black people loved the guitar version."
Run–D.M.C. were the rare teenagers who were willing to take advice from their elders; Smith was the most successful rap producer at that point, having produced Kurtis Blow and Whodini. He produced the first two Run–D.M.C. albums.