Led Zeppelin often borrowed from American blues recordings, and the guitar riff in this song bears a strong resemblance to the 1961 Bobby Parker song "Watch Your Step
." Led Zeppelin has faced criticism for using parts of obscure folk and blues songs and passing them off as their own, but it should be noted that riffs cannot be copyrighted, and many famous musicians have borrowed in a similar fashion. A notable example is The Beatles "I Feel Fine
," which was also influenced by Parker's "Watch Your Step."