Paranoid is notable for its aggressive and darker tone, delving deeper into themes of war, social anxiety, and the supernatural. Tracks like "War Pigs" and "Paranoid" themselves tackle heavy subjects, with "War Pigs" critiquing the glorification of war and the politicians who wage it, while the title track captures a sense of anxiety and desperation. The album's lyrics were a significant departure from the more straightforward rock themes of the time, resonating with a generation disillusioned with mainstream culture.

: A heavy, anti-war anthem that serves as the album's opening statement.

: The title track was an afterthought, written in roughly 20 minutes to fill space on the record. It became the band's signature hit.