WARNING: This article contains spoilers for Spider-Man: Far From Home, in theaters now.

Avengers: Endgame may have featured the climactic ending to the Marvel Cinematic Universe's sprawling Infinity Saga, but Spider-Man: Far From Home serves as the final film of Phase 3. As a much quieter affair, Far From Home is almost an epilogue of sorts that brings closure to the events of Endgame and it opens up the doors to the future.

Therefore, as both an ending and a new beginning, it's quite fitting that this film features an incredibly emotional and brilliant callback to the opening seconds of 2008's Iron Man, which kicked off the entire MCU.

RELATED: Spider-Man: Far From Home Cements Tony Stark's True MCU Legacy

Tom Holland Peter Parker Costume in Far From Home

As fans will recall, the MCU was born with the arrival of Jon Favreau's first Iron Man. The film opens in Afghanistan, as Tony Stark's military motorcade drives through the desert. Before we even see the genius-billionaire-playboy-philanthropist, AC/DC's "Back In Black" plays, instantly setting a tone for not just the movie, but the character himself. Throughout his appearances in Iron Man 2 and 2012's The Avengers, AC/DC's music would always accompany Iron Man's entrances, to the point that the rock band's songs became a signature of sorts for the Armored Avenger.

It's been more than seven years since the MCU featured AC/DC's music, but it finally makes a triumphant return in Spider-Man: Far From Home, and it's not just any AC/DC song.

In the Jon Watts-directed sequel, Peter Parker finds himself trying to live up to the legacy of Tony Stark. People keep asking him if he will be the new Iron Man, and he simply doesn't have the answers. He just wants to be a kid, and go on his school trip with the girl he really likes. But after a brutal battle against Mysterio, Peter finds himself reeling.

Tom Holland Sad Peter Parker Spider-Man Far From Home

Talking with Happy Hogan aboard a Stark Industries plane, Peter breaks down in a heartbreaking scene where he reveals that he misses Tony and that he has no idea how to live up to his legacy. However, an uplifting pep talk from Happy inspires Peter to get back up, assume his heroic responsibilities and fight on. Resolved to defeat his enemy, Peter walks into the plane's workshop to build himself a new suit.

"You take care of the suit," Happy says, "and I'll take care of the music." Then, as Peter starts designing his new suit with the help of holograms, AC/DC's "Back In Black" starts to blast through. Even though Peter incorrectly believes that he's listening to Led Zeppelin, fans will recognize this as Iron Man's unofficial theme song.

RELATED: How Spider-Man: Far From Home Addresses the MCU's Five-Year Gap

The use of the song resonates in an emotional manner, and it also offers a powerful message. It signals that Peter is his own hero now. He can't live up to Iron Man, but he can be Spider-Man, a new, different kind of hero for a new generation. It's a brilliant, brief nod to the start of the MCU, as Peter assumes his role as the new face of this sprawling universe.

Thanks to the song, everything comes full circle -- but it also signals that we are witnessing a fresh start. "Back In Black" launched the MCU in 2008 and now, 11 years later, it continues to propel the universe into its next iteration.

Now in theaters, director Jon Watts’ Spider-Man: Far From Home stars Tom Holland, Samuel L. Jackson, Zendaya, Cobie Smulders, Jon Favreau, JB Smoove, Jacob Batalon and Martin Starr, with Marisa Tomei and Jake Gyllenhaal.