Black Sabbath had just tapped into a vicious hot streak on the album before this, so the anticipation for this album was quite high. Opening with a few seconds of a harsh cough (the sound of Tony Iommi choking on a joint between recording sessions), one of the greatest guitar riffs ever committed to record suddenly jumps out of the speakers and lays down its mid-tempo groove with gleeful abandon. Few bands outside of the psychedelic movement had professed their love for marijuana, but Sabbath avoided the hypnotic approach of those bands and went straight for the gut with their song. Boasting incredibly simplistic lyrics, Osbourne sounds downright happy as he tells the world how drugs have enhanced his life and introduced him to his mind. This may not be the healthiest message to preach, but the delivery spoke louder to the working-class metal fans they were catering to than any Country Joe and the Fish song ever could. And the music is brilliant, featuring a guitar part that was so great it would go on to fuel the Beastie Boys' "Rhymin' and Stealin'," the Butthole Surfers' manic tribute "Sweet Loaf," and the last 30 seconds of the Red Hot Chili Peppers's "Give It Away," among others. On top of that, artists as diverse as Mogwai, Sacred Reich, and Ugly Kid Joe would also cover it, making it one of the best-known tracks in their canon. In one song, the band managed to prove that metal can be fun, heavy doesn't always mean evil, and drugs aren't just for hippies and artists. Most of that is common knowledge now, but Sabbath was writing this in a time when metal was still considered a fad and critics tried to ignore the strides they were making. "Sweet Leaf" is maybe only below "Paranoid" in terms of the affect it would have on the genre, and it has a much better riff to boast.