Songfacts®:

• "You Must Burn!" takes aim at the controversial phenomenon of cancel culture. Over chugging instrumentals, frontman James Hetfield draws attention to the dangers of mob mentality and the perils of judgment without due process. Drawing allusions to historical events such as the Salem Witch Trials and the Spanish Inquisition, Hetfield highlights the tragic consequences of overreaction and mindless condemnation.
  
  Smile as it burns to the ground
  The perfect don't want you around
  Question yourself, you may learn
  You are the witch, you must burn
• The song continues the themes present in Metallica's 1991 Black Album track "Sad But True" and features a similar style.
• Metallica bass player Robert Trujillo sings on the bridge, a rare appearance on the mic for him (he did sing backup on their 2016 song "Dream No More"). This shows how Metallica was willing to experiment with new sounds and ideas at the time - singing is way out of Trujillo's comfort zone.
• Trujillo was surprised when co-producer Greg Fidelman told him he was going to get him to sing. "I was, like, 'Really?' I got a little nervous. At the same time, I was very motivated," he said in an interview with the Metallica fan magazine So What!. "Fortunately for me, the part really does suit my comfort zone, so to speak. The vibe and the interesting - I don't know, I wouldn't say the 'quality' in what I had to offer, but the part lends itself to my personality, to my voice, and it sits and slots in really well with the moment and bass breakdown. So it's cool that it's this breakdown that James and I were able to jam on and create, and then I get to sing on it too."
• Regarding how "You Must Burn!" came together musically, Trujillo described how the song evolved from a simple idea in the band's tuning room to a moody, atmospheric piece with a distinct feel and vibe. "It starts to take shape, it kind of builds itself, and then at some point, it finds its way," he said, "With this particular middle section that came to be, that was really centered around a jam and was very moody, and there's a danger to it; I like how the bass is walking. It's got a feel to it where it's 'walking through a forest,' like a scene from a Tim Burton movie or something. That's the feel I get. And James and I just started kind of grooving on it. It was just the two of us. That was a special moment for me because whenever I can find that magic carpet with James, it's really a lot of fun. You know, we just sync in; it's like we're riding this wave together."
  
  Trujillo added that Metallica's 2008 Death Magnetic track, "Suicide & Redemption," was born in a similar way during a jam session in South Africa. "I started playing the pulsating bass line," he said. "Then he started to hit these power chords, kind of counterpoint and tension chords, stuff like that. So it's always fun when you find that moment where something starts to work."
• "You Must Burn!" is only the second Metallica song with an exclamation point in the title. The first was "Atlas, Rise!" from 2016's Hardwired… To Self-Destruct.
• Trujillo's vocal harmonies on "You Must Burn" create an otherworldly and haunting atmosphere.
  
  "We wanted something ethereal or dreamy for that part, a juxtaposition to what was going on in the rest of the song, "Ulrich explained to Rolling Stone.
  
  "We wanted something that didn't feel so much like a vocal, middle-eight type thing but some atmospheric element to it. And Robert stepped up and added his part to that. So, it has a sound all its own both from the creative part of it and the execution part of it."
• The middle section of "You Must Burn!" grew out of an idea Robert Trujillo developed that was directly inspired by Ozzy Osbourne's 1981 song "Believer," particularly its sliding feel and heavy power groove. Trujillo noted to Metal Hammer that when he recorded his vocal part on "You Must Burn!" he consciously tried to "channel Ozzy," further underlining the connection.