Speaking with Guitar World in a 2002 interview, Kirk Hammett explained how he came up with the guitar melody in this track. "I tracked the whole album with Marshall amps and my Gibson Flying V," the Metallica axeman explained. "For that song, I knew that I wanted to come up with something really melodic at the beginning of the solo. At that point in the song, there's just a lot of riffing, a lot of heavy dynamics. I was thinking, 'Wouldn't it be nice if we had something somewhat melodic to lead into it?' Hence that little melody I played… It was our first instrumental, and it was an incredibly long guitar solo. It was like, 'How can I keep this solo going without making it sound like I'm just playing a bunch of notes?' So I thought that I would break it up into sections rather than play one long spew of notes.
I used a modal approach, and there's also arpeggios that I play in the solo – they're actually 'broken arpeggios,' a term that I got from Yngwie Malmsteen. At that time, 1984, Yngwie was big in the guitar world; he influenced me in that he was using all these different scales and different arpeggios, and really got me thinking about that kind of sound. I was also thinking chromatically: there's that one part at the top of the next cycle where I play a chromatic lick that goes all the way down the high E string with the wah pedal.
I actually wrote out the entire solo on pieces of paper, using my own notes and my own pet names for the individual licks. I would say that 80 percent of it was composed beforehand and 20 percent of it was improvised. When we revisited that song with the symphony on S&M, it was a lot of fun; it felt like I was visiting my guitar technique from, like, 15 years ago or something. I just don't play like that now – I'm a lot bluesier – so it was pretty trippy."