Who the glove belongs to remains a mystery, but on the Russo brothers' Facebook page fans speculated it might be Captain America's or it could mean an appearance from the Fantastic Four (whose film rights remain with Fox Studios).
The cinematic universe (called MCU or Marvel Cinematic Universe) started with Robert Downey Jr starrer Iron Man, a successful 2008 film and there have been 16 films so far that have been released till Spider-man: Homecoming. The director duo posted a teaser photo on social media marking the beginning of Avengers 4 shoot. The enormous cast features mainstays like Captain America (Chris Evans) and Iron Man (Robert Downey Jr.), newer characters like Spider-Man (Tom Holland) and Black Panther (Chadwick Boseman), the Guardians of the Galaxy (Chris Pratt, Zoe Saldana, Dave Bautista, Bradley Cooper, Vin Diesel, Pom Klementieff), and many more. The cast of the movie is being kept a secret out of fear of revealing too much about the events of Infinity War, where it has been rumored that not everybody will make it to Avengers 4 after battling the Mad Titan.
"Avengers 3" and "4" will follow Earth's Mightiest Heroes teaming up with the Guardians of the Galaxy to face off against evil Thanos and the Black Order.