Thanos’ full fledged arrival in the Marvel Cinematic Universe has been anticipated by the fandom for years.
Its this accessory of destruction that will bring Thanos to Earth, as he’s attempting to reclaim all of the Infinity Stones- one of which is in Vision’s forehead.
From there, he briefly showed up in the first Guardians of the Galaxy, and had another cameo in Avengers: Age of Ultron, where he managed to accrue his Infinity Gauntlet.
He was first teased way back in 2012’s The Avengers.