[WARNING: This article contains spoilers for episodes 8 and 9 of Stranger Things 4 on Netflix!]

When part one of Stranger Things season 4 made its debut earlier in June, everyone opened up “Running Up That Hill” on Spotify. Now that part two has officially premiered, another classic 80’s song has made its debut with the Stranger Things crew. That song is “Master of Puppets” by Metallica.

“Running Up That Hill” played a vital role in season 4, in that it saved Max’s (Sadie Sink) life when Vecna (Jamie Campbell Bower) practically had her in his claws. But listening to Kate Bush and remembering her friends, Max regained the will to run and literally jumped back to her friends. “Master of Puppets” almost serves an opposing role for the character Eddie Munson (Joseph Quinn). The scene in which the song premieres is when he and Dustin serve as bait, grabbing the attention of Vecna (and his army of monster bats) while Nancy (Natalia Dyer), Steve (Joe Keery), and Robin (Maya Hawke) sneak into the house to kill him while he’s in a trance-like state.

Dustin (Gaten Matarazzo) and Eddie barricade Eddie’s trailer in the upside down and find his electric guitar, with which Eddie performs the song on the trailer’s roof. Metallica, the upside down, and demonic bats, it’s enough to make audiences raising the horns on their couches at home! But when putting the scene together, the Duffer Brothers were well aware that in order to get the scene right, they had to tread cautiously.

“Master of Puppets” is the only single from the album of the same name, and considered a holy classic of Metallica’s long library of music. James Hetfield, leader vocalist of the band, has gone on record for stating that the song is essentially about drugs and addiction. But with lyrics about literal pulling strings, the song is a testament to the struggle for control. A fitting choice to pair with Vecna’s childhood fascination with spiders. Nora Felder, music supervisor for Stranger Things, spoke with Variety about how the Duffer Brothers integrated the song into the script.

“It was another one of those ‘it has to be this song,’ moments. This part of the story was anticipated to be a pivotal and especially hair-raising scene in which Eddie heroically stood tall for the fight of his life. I believe the Duffer Brothers felt that playing ‘Master of Puppets’ throughout the extended scene was the clear choice. No other song was discussed further, and we jumped in to clear it straight away. The track was a perfect match for Eddie since it not only amplified the episode’s most thrilling scene, but “in some ways, aligns with Eddie’s seemingly arrogant and edgy in-your-face public persona.”

Related: Sadie Sink Unsure of Max's Fate in Stranger Things Season 5

Pleasing the First Puppetmasters…

Vecna Stranger Things Season 4
Netflix 

Now that they had the script, it was time for the tricky step. Metallica still needed to sign through on the rights to feature their song. Felder said that all clearances had to go directly through the band. She goes further into detail on the tension of the negotiations.

“I got in touch with Metallica’s management office and carefully went over the scene and what the intent would be. I knew the clearance would be taken seriously as we had used one of their songs (‘The Four Horseman’) in season 2 and had learned at that time that they were fans of the show. ‘Master of Puppets’ is a pretty significant song in their catalog, and I think it’s considered a favorite in their live shows. I wanted to be respectful in making sure that Metallica fully understood what context the song was being used in, plus how integral it was to the scene and for this exciting new character, Eddie Munson, who no one had met yet in previous seasons.”

Playing their cards so carefully won off in the end. The band signed off on the pitch, giving the team the okay to use the song. Felder also went on to confirm that Quinn’s playing was authentic in the scene.

“Yes, Joseph did take time to learn the guitar riff and was actually playing along to a guide track. Everyone thought he did a great job.”