Avengers: Endgame makes use of some music Star-Lord would approve of. Infinity War broke from tradition and featured one song other than Alan Silvestri's original score, which was "Rubberband Man" by the Spinners and it was used to introduce the Guardians of the Galaxy. It was a perfect way to keep the fun atmosphere director James Gunn created with the use of pop music in the Guardians franchise, but it also foreshadows the arrival of Thanos and his plan to use his mighty snap, much like the opening song in Endgame. There are MAJOR SPOILERS for Avengers: Endgame below.
Avengers: Endgame begins with Tony Stark and Nebula stranded in space aboard the Benatar while Traffic's 1967 hit song "Dear Mr. Fantasy" is playing over the Marvel logo. Stark and Nebula are playing a paper football game to pass the time while presumably finding the song on Star-Lord's Zune MP3 player. First of all, the vibe of the song is perfect and completely out of place for an Avengers movie. With that being said, it would have fit in really well on the Guardians of the Galaxy 2 soundtrack.
However, upon listening closer, one can see how the song might foreshadow a bit of Tony Stark's story arc in Avengers: Endgame and the MCU as a whole. This has to be a song that was placed on Star-Lord's Zune, which in turn gives us the Guardians of the Galaxy vibe, but melancholic as opposed to upbeat. Much like "Rubberband Man" possibly being the arrival of Thanos, Traffic's "Dear Mr. Fantasy" provides some pretty interesting lyrics pertaining to Endgame and in particular, Stark. You can read a sample below.
"Dear Mr. Fantasy play us a tune, Something to make us all happy, Do anything, take us out of this gloom, Sing a song, play guitar, make it snappy. You are the one who can make us all laugh, But doing that you break out in tears, Please don't be sad if it was a straight mind you had, We wouldn't have known you all these years"
It's not too big of a stretch to think of Tony Stark as being Mr. Fantasy in the song. Though reluctant, Stark is the one who finally figures out the time travel conundrum through the use of the Quantum Realm to allow the "time heist" to occur. He is the one making everybody happy and he's setting forth to take the universe out of its "gloom" that Thanos created. Obviously, he doesn't sing or play guitar, but his brain is behind the technology to save the universe. Finally, it's Stark who takes the Infinity Stones and snaps away Thanos and his army, sacrificing his life in the process. The song is almost like a goodbye to Stark and a thank you letter.
Traffic's "Dear Mr. Fantasy" is also deceptively simple in terms of arrangement and presentation, but later gets into a much different territory from where it started, much like the original plan in Avengers: Endgame. Nothing is ever this literal, but it's easy to see why the Russo Brothers went with the song for the opening. The movie also features Steppenwolf 's song "Hey Lawdy Mama," which plays during Stan Lee's cameo, The Kinks song "Supersonic Rocket Ship," and Redbone's "Come and Get Your Love" is also reused from Guardians of the Galaxy. You can check out Traffic's "Dear Mr. Fantasy" from Avengers: Endgame below, thanks to the Walt Disney Pictures Music YouTube channel.