But if you've been away from the MCU, catching up can feel daunting. Whether you're a longtime fan or a first-time viewer preparing for Avengers: Doomsday, this guide breaks down the essential Marvel movies and series to watch—in the right order. What to watch: Your definitive MCU watch guide before Avengers: Doomsday1. Birth of the Avengers​Movies that introduce the original heroes and lay the foundation of the MCU. The MCU expandsThe Avengers grow stronger as new heroes, magical forces and cosmic threats expand the MCU beyond Earth.