Thanos (Josh Brolin) has the ambition to collect six immortal stones scattered in various places. Each stone has its own strength so not just anyone can get it.
If you already have the six immortal stones, Thanos can become the ruler of the universe. Thanos also intends to eliminate half the population of the universe because it is believed to be able to make life more prosperous.
Thanos and his men spread terror while looking for the stones. The cruelty of Thanos was witnessed by Bruce Banner / Hulk (Mark Ruffalo) and Thor (Chris Hemsworth). They intend to find another superhero in order to prevent Thanos' ambition.
The Hulk returns to Earth and tells Thanos to act on Tony Stark / Iron Man (Robert Downey Jr.), Doctor Strange (Benedict Cumberbatch) and Wong (Benedict Wong). Unfortunately, Thanos appeared before they could go any further.
As a result, Iron Man and Doctor Strange entered the Thanos spaceship. The chaos increases when Peter Parker / Spider-Man (Tom Holland) takes them along.
Meanwhile Thor is rescued by members of the Guardians of the Galaxy. Thor believes that he can only save Thanos with the help of his powerful hammer. Together with Rocket (voiced by Bradley Cooper) and Groot (voiced by Vin Diesel), Thor goes to another planet to get a new magic hammer.
As Thor and Hulk plot, Thanos's men go after Vision (Paul Bettany). One of the immortal stones resides in Vision's body. Realizing that his girlfriend's life is being threatened, Wanda Maximoff / Scarlet Witch (Elizabeth Olsen) asks Steve Rogers / Captain America (Chris Evans), Natasha Romanoff / Black Widow (Scarlett Johansson), and Sam Wilson / Falcon (Anthony Mackie) to help them.
Captain America then takes them to Wakanda and meets T'Challa / Black Panther (Chadwick Boseman) and Bucky Barnes / Winter Soldier (Sebastian Stan). Captain America feels Wakanda is a safe place. Wakanda also has sufficient troops to be able to face war.
Then where is Thanos? The villain is forcing his stepdaughter, Gamora (Zoe Saldana) to show the location of one of the immortal stones. This makes Peter Quill / Star-Lord (Chris Pratt), Drax (Dave Bautista), and Mantis (Pom Klementieff) determined to save him.