I got a question for you: "Bad" is a song by rock band U2 and the seventh track from their 1984 album, The Unforgettable Fire. A song about heroin addiction, it is considered a fan favourite, and is one of U2's most frequently performed songs in concert.

Answer this question: what is the song bad about by u2?
Let's think first:
To answer the above question, the relevant sentence is: A song about heroin addiction, it is considered a fan favourite, and is one of U2's most frequently performed songs in concert.
Therefore, the answer is heroin addiction.