Paranoid is a song by Black Sabbath, coming from an album of the same name. Supposedly, the members of Black Sabbath put together this song in 15 minutes based off a riff by Tony Iommi. This song was only meant to be a "filler", but became one of Black Sabbath's most successful songs. The record company changed the album's name from War Pigs, as it was originally intended, to Paranoid in order to identify it with the song, which would be released as the single.

Clocking at less than 3 minutes, and uncharacterisicaly fast and simple for a Black Sabbath song, it has been widely covered by bands from Punk to Heavy Metal, including Megadeth.

The initial riff of Paranoid

  3|-----------------------|
  4|------------7-9----7-9-|
  5|-9-9-9--7-9-----7-9----|
  6|-7-7-7-----------------|

is very similar to the riff of Dazed and confused by Led Zeppelin and its chords resemble those of What is and what should never be (by Led Zeppelin too):

  3|---------------------------12----------12|
  4|14xxxxx--12xxxxxxxxxxxxxx--12--12--14--12|
  5|14xxxxx--12xxxxxxxxxxxxxx--10--12--12----|
  6|12xxxxx--10xxxxxxxxxxxxxx------10--12----|
  'Cause she couldn´t help me with my mind