The footage popped up during the Marvel Studios Live-Action panel, and you can read the description below from ComicBook.com's Brandon Davis, who is attending the event.
"Avengers tower comes into frame. Clips from The Avengers, Captain America: The Winter Soldier, Guardians of the Galaxy, Vol. 2, Doctor Strange, Iron Man, Avengers: Age of Ultron, Captain America: The Winter Soldier, Thor, Thor: The Dark World, Iron Man 2, and Iron Man 3 play."
Then the new footage begins.
"'We are arriving,' Mantis said to the Guardians. Teenage Groot in a seat. They describe this place as 'dangerous.' The body of Thor lands on their windshield. His hair is short. Rocket is startled. Mantis wakes him up using her powers. Thor is startled. All of the Guardians look at him, prompting him to ask who they are. The ship zips through the cosmos. Elsewhere, Wanda dodges some white energy, and it breaks a truck. Somewhere else, Loki stands in ruin, presenting the Tesseract to someone. Peter's Spider-Sense takes off as he rides a bus. Tony prepares for battle. He is in space with the Guardians.
"'Fun really isn't something one considers when balancing the universe,' Thanos said. 'This does put a smile on my face.' Gamora looks on, terrified. The Guardians observe ruin in many places across Earth and the cosmos. Thanos warps into this new world. Star-Lord battles him. Strange battles him. Spider-man, in his new suit, battles him. Winter Soldier battles on Earth. Wakanda readies to defend their territory. Cap steps out of the shadows, bearded, with longer hair. Hulkbuster fights.
"Peter looks up at Tony, laying down with his mask off, fighting tears with Tony's hand behind his head, and says, 'I'm sorry, Tony.'
"Black Panther fights an Outrider, appearing as it did Infinity. Thor's head is squeezed by Thanos. Thanos pummels Iron Man in a fight. The Guardians are all defeated. Thanos has assembled the Infinity Gauntlet. He throws a moon at an entire planet."
As you can see
“It needs no teasing,” Holland said to the Toronto Sun. “That movie literally needs no teasing. It’s going to be the biggest movie of all time. Believe me; no one is ready for that movie. I don’t know anything about it or what it’s about.”
In addition to Spider-Man, Infinity War will also bring in Black Panther, the Guardians of the Galaxy, Doctor Strange, Ant-Man, Thor, Hulk, and
Avengers: Infinity War currently has a 4.34 out of 5 on ComicBook.com's anticipation rankings, which you can submit your vote for here. The description for Infinity War is included below.
Avengers: Infinity War is described by Marvel Studios as the culmination of everything in the Marvel Cinematic Universe since Iron Man in 2008. The movie is filming now under directors Anthony and Joe Russo, from a screenplay by Christopher Markus and Stephen McFeely.
The expansive confirmed cast includes Robert Downey, Jr., Chris Evans, Chris Hemsworth, Mark Ruffalo, Jeremy Renner, Scarlett Johansson, Tom Holland, Elizabeth Olsen, Paul Bethany, Sebastian Stan, Benedict Cumberbatch, Benedict Wong, Chris Pratt, Zoe Saldana, Karen Gillan, Vin Diesel, Dave Bautista, Bradley Cooper, Pom Klementieff, and Josh Brolin as the villain Thanos.
Guardians of the Galaxy Vol. 2 and Spider-Man: Homecoming
MORE AVENGERS: INFINITY WAR: Infinity War Has Officially Wrapped Production / D23 - First Look At Thanos, Black Panther, Star Wars, And More / What Could Be Hiding Behind Thanos At The Marvel Studios Booth?