Being one of Led Zeppelin's most recognizable songs, "Black Dog" is a great example of taking a seemingly simple riff and warping into into something incredibly unique. "Black Dog" just seems to ebb and flow throughout the different sections.
The unusual rhythm for the song was accomplished by drummer John Bonham keeping count for the band by clicking his drumsticks together during the quite sections. If you turn it up loud enough you can actually hear it on the original recording. Partly because of this unique feel "Black Dog" has long been a Led Zeppelin fan favorite.
Jimmy Page's rhythm parts are almost like solos in themselves with the way he continuously creates rhythmic single note lines throughout the song. The signature main riff was actually credited to John Paul Jones, but Jimmy Page seems to take it and run with it. His solo during the outro section of the song uses a TON of signature Jimmy Page licks including rapid pentatonics and smooth oblique bends.
"Black Dog" is truly a masterpiece of classic rock and pure signature Led Zeppelin throughout. Good luck!!