At this point, there's little question that Avengers: Infinity War will be the biggest Marvel Cinematic Universe movie to date. The film will bring all corners of the MCU together in one massive event, and it looks like we can expect to see elements of every Marvel movie scattered through the story. In fact, Kevin Feige and Joe Russo both addressed this culmination during the "Marvel Studios: The First Ten Years - The Evolution of Heroes" special feature segment on Thor: Ragnarok's home release and laid out how every Marvel movie will feed into the Infinity War storyline. Russo explained:
Every story that Marvel has told since Iron Man 1 finds a narrative thread in these next two Avengers movies. It is a culmination of all that storytelling.
So, it seems that everything from Iron Man through Black Panther will have some degree of relevance to the next two Avengers movies. Even movies with seemingly minimal connections to the bigger Marvel universe (such as Ant-Man) will factor into how Avengers: Infinity War will play out. Though we still technically have no idea what that will ultimately entail (or how big each narrative thread will eventually be), it seems to suggest that Infinity War may be one of Marvel's most dense and detail-oriented movies yet. You might want to go back and refresh yourself on all 18 movies before May 4 rolls around. (Good luck with that.)
As exciting as Joe Russo makes it sound, Kevin Feige's take on the situation arguably seems even more thorough. Addressing the comprehensive nature of the Infinity War arc, the Marvel Studios president also made it clear that Avengers: Infinity War will wrap things up and push the MCU forward in a "new direction." Per Feige:
With Infinity War, we are paying off every little thread, every little tease, that we've had in what will be 18 films prior to Infinity War. There's never been anything like this. Being able to, film after film, tease at a larger story. Really building these stories up until a conclusion, while at the same time, introducing an entirely new direction for the future.
That idea is interesting to note because it looks like Avengers: Infinity War will lay plenty of groundwork in addition to paying off the first three phases. While movies like Iron Man, Captain America: Civil War, and other MCU classics receive nods, the film will also shuffle the deck in ways that will allow the folks behind these Marvel movies to try new things going into Phase 4.
You can check out the "Marvel Studios: The First Ten Years - The Evolution of Heroes" segment on Thor: Ragnarok's home release, which is currently available on Digital HD and will release on Blu-ray and DVD on March 6. Looking ahead, make sure to keep an eye on all of these story threads when Avengers: Infinity War premieres in theaters on May 4.
