premise: "Enter Sandman" is a song by American heavy metal band Metallica. It was released as the first single from their eponymous fifth album, "Metallica" in 1991. The music was written by Kirk Hammett, James Hetfield and Lars Ulrich. Vocalist and rhythm guitarist Hetfield wrote the lyrics, which deal with the concept of a child's nightmares.
hypothesis: Metallica released four albums before Metallica.
reason: Metallica is the fifth album. The system was confused by the names.