Which UNSC sergeant joins Master Chief in Operation METEORITE?

The UNSC sergeant who joins Master Chief in Operation METEORITE is Avery Johnson.

More precisely, the character is Sergeant Major Avery Johnson, one of the most recognizable soldiers in the Halo universe. The new missions use his partnership with Master Chief to explore a period of their service that was not shown in the original Halo: Combat Evolved campaign.

Johnson is already a veteran when the main game begins. He serves as a tough, charismatic UNSC leader who repeatedly works alongside the Chief against the Covenant. His appearances span the original trilogy, making him much more than a supporting Marine encountered in one mission.

The other choices are characters from the wider Halo cast but do not fill this role. Thomas Lasky becomes a major UNSC commander later in the series, Miranda Keyes is Captain Jacob Keyes’s daughter and a commander in Halo 2, and Jacob Keyes is the captain of the Pillar of Autumn in Combat Evolved. None is the sergeant paired with Chief in this prequel arc.