Question: Which song did Metallica release in 1991 from their fifth album that is one of their most well known?

full_context: Document 1: Kill 'Em All: Kill 'Em All is the debut studio album by the American heavy metal band Metallica, released on July 25, 1983, by the independent record label Megaforce Records. "Kill 'Em All" is regarded as a groundbreaking album for thrash metal because of its precise musicianship, which fuses new wave of British heavy metal riffs with hardcore punk tempos. The album's musical approach and lyrics were markedly different from rock's mainstream of the early 1980s and inspired a number of bands who followed in similar manner. The album did not enter the "Billboard" 200 until 1986, when it peaked at number 155, following Metallica's commercial success with its third studio album "Master of Puppets"; the 1988 Elektra reissue peaked at number 120. "Kill 'Em All" was critically praised at the time of its release and in retrospect, and was placed on a few publications' best album lists. It was certified 3× Platinum by the Recording Industry Association of America (RIAA) in 1999 for shipping three million copies in the United States. The album generated two singles, "Whiplash" and "Jump in the Fire".
Document 2: Ride the Lightning: Ride the Lightning is the second studio album by American heavy metal band Metallica, released on July 27, 1984, by the independent record label Megaforce Records. The album was recorded in three weeks with producer Flemming Rasmussen at the Sweet Silence Studios in Copenhagen, Denmark. The artwork, based on a concept by the band, depicts an electric chair being struck by lightning flowing from the band logo. The title was taken from a passage in Stephen King's novel "The Stand". Although rooted in the thrash metal genre, the album showcased the band's musical growth and lyrical sophistication. This was partly because bassist Cliff Burton introduced the basics of music theory to the rest of the band and had more input in the songwriting. Instead of relying strictly on fast tempos as on its debut "Kill 'Em All", Metallica broadened its approach by employing acoustic guitars, extended instrumentals, and more complex harmonies. The overall recording costs were paid by Metallica's European label Music for Nations because Megaforce was unable to cover it. It was the last album to feature songwriting contributions from former lead guitarist Dave Mustaine.
Document 3: Mama Said (Metallica song): "Mama Said" is a power ballad by American heavy metal band Metallica from their sixth album "Load", with music and lyrics by James Hetfield (music credited to Hetfield/Ulrich). The lyrics represent a man or boy who is learning to find his own way in life away from his mother. The song is directly written about Hetfield's difficult relationship with his mother, who died of cancer when he was 16 years old.
Document 4: Load (album): Load is the sixth studio album by the American heavy metal band Metallica, released on June 4, 1996 by Elektra Records in the United States and by Vertigo Records internationally. The album showed more of a hard rock side of Metallica than the band's typical thrash metal style, which alienated much of the band's fanbase. It also featured influences from genres such as Southern rock, blues rock, country rock and alternative rock. Drummer Lars Ulrich said about "Load"'s more exploratory nature, "This album and what we're doing with it – that, to me, is what Metallica are all about: exploring different things. The minute you stop exploring, then just sit down and fucking die."
Document 5: Metallica (album): Metallica (commonly known as The Black Album) is the fifth studio album by American heavy metal band Metallica. Released on August 12, 1991 by Elektra Records, it received widespread critical acclaim and became the band's best-selling album. "Metallica" produced five singles that are considered to be among the band's best-known songs, which include "Enter Sandman", "The Unforgiven", "Nothing Else Matters", "Wherever I May Roam", and "Sad but True". "Don't Tread on Me" was also issued to rock radio shortly after the album's release, but the song did not receive a commercial single release. The album marked a change in the band's sound from the thrash metal style of the previous four albums to a slower one. Metallica promoted the album with a series of tours. In 2003, the album was ranked number 252 on "Rolling Stone"' s 500 greatest albums of all time.
Document 6: St. Anger: St. Anger is the eighth studio album by American heavy metal band Metallica, released on June 5, 2003, by Elektra Records. It was the band's last album released through Elektra, and the second-longest timespan between studio albums from Metallica, with nearly six years between the release of "Reload" and this album. It is also the final collaboration between Metallica and producer Bob Rock, whose relationship began with the band's fifth studio album, 1991's "Metallica". "St. Anger" was originally intended for release on June 10, 2003, but was released five days earlier due to concerns over unlicensed distribution through peer-to-peer file sharing networks. The "St. Anger" sessions also mark the only time Rock played when the music was being recorded, filling in for the departed bassist Jason Newsted.
Document 7: Nothing Else Matters: "Nothing Else Matters" is a song by American heavy metal band Metallica. It was released in 1992 as the third single from their self-titled fifth studio album, "Metallica". The song peaked at number 11 on the "Billboard" Mainstream Rock Tracks chart as well as top-ten positions on many European charts. "Nothing Else Matters" was featured as a playable track in the music video game "". Recognized as one of Metallica's best known and most popular songs, it has become a staple in live performances. The song has been covered nearly 100 times.
Document 8: Creeping Death: "Creeping Death" is a song by the American heavy metal band Metallica, released as the lead and only commercial single from their second studio album "Ride the Lightning" (1984) ("Fade to Black" and "For Whom the Bell Tolls", from the same album, were issued as promotional singles). Written from the perspective of the Angel of Death, it describes the (Exodus 12:29). One of Metallica's most frequently performed songs, it has been played live 1,458 times (third only to "Seek & Destroy" at 1,484 and "Master of Puppets", at 1,553), and it has occasionally been used on various tours as the opening song of the band's set. It stands as a classic example of the band's thrash style, albeit slower than the material on their first album, "Kill 'Em All". The song's middle section, with its ominous chants of "Die!" set to a phrygian mode chord progression, is a fan participation staple during Metallica shows.
Document 9: Wherever I May Roam: "Wherever I May Roam" is a song by American heavy metal band Metallica. It was released in October 1992 as the fourth single from their eponymous fifth album, "Metallica".
Document 10: Metallica: Metallica is an American heavy metal band based in San Rafael, California. The band was formed in 1981 in Los Angeles when vocalist/guitarist James Hetfield responded to an advertisement posted by drummer Lars Ulrich in a local newspaper. Metallica's current lineup comprises founding members Hetfield and Ulrich, longtime lead guitarist Kirk Hammett, and bassist Robert Trujillo. Guitarist Dave Mustaine (who went on to form Megadeth) and bassists Ron McGovney, Cliff Burton, and Jason Newsted are also former members of the band.
Document 11: James Hetfield: James Alan Hetfield (born August 3, 1963) is an American musician, singer, and songwriter known for being the co-founder, lead vocalist, rhythm guitarist, and main songwriter for the American heavy metal band Metallica. Hetfield is mainly known for his intricate rhythm playing, but occasionally performs lead guitar duties and solos, both live and in the studio. Hetfield co-founded Metallica in October 1981 after answering a classified advertisement by drummer Lars Ulrich in the Los Angeles newspaper "The Recycler". Metallica has won nine Grammy Awards and released ten studio albums, three live albums, four extended plays and 24 singles.
Document 12: The Unforgiven (song): "The Unforgiven" is a power ballad by American metal band Metallica. It was released as the second single from their eponymous fifth album "Metallica" (also known as "The Black Album"). Though one of the slower tracks on the album, its chord progression is distinctly one of the heavier. The song deals with the theme of the struggle of the individual against the efforts of those who would subjugate him.
Document 13: Metallica discography: The following is the discography of Metallica, a Los Angeles-based metal band formed in 1981 by James Hetfield (lead vocals, rhythm guitar) and Lars Ulrich (drums). After several bassist and lead guitarist changes, the band settled on Cliff Burton and Kirk Hammett, respectively. Metallica started playing locally, releasing their first widely circulated demo, "No Life 'til Leather", in 1982. The demo caught the attention of Johny Zazula, who signed Metallica to Megaforce Records. The band released "Kill 'Em All" in 1983, and the following year they released "Ride the Lightning". After "Ride the Lightning" was released, Metallica left Megaforce and signed to Elektra Records. In March 1986, the band released its third studio album, "Master of Puppets", which was Metallica's first album to be certified gold by the Recording Industry Association of America (RIAA). While promoting the album, Burton was killed in a bus accident. Jason Newsted was hired as a replacement. The band's first release to feature the new member was "," and then followed by "...And Justice for All" in August 1988, which peaked at number six on the "Billboard" 200.
Document 14: Enter Sandman: "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.
Document 15: List of songs recorded by Metallica: Metallica is an American heavy metal band formed in Los Angeles, California in 1981. The band released its debut album "Kill 'Em All" in 1983, which credited songwriting between frontman James Hetfield, drummer Lars Ulrich and guitarist Dave Mustaine, who had left before the album was recorded (bassist Cliff Burton was credited for the bass solo "(Anesthesia) – Pulling Teeth"). On the 1984 follow-up "Ride the Lightning", Burton received more songwriting credits and Mustaine's replacement Kirk Hammett was also co-credited on four songs. "Master of Puppets", released in 1986, was the last album to feature Burton, who died in a bus accident later that year.
ground_truth: Enter Sandman