Several projects have surfaced over the years, aiming to bring co-op or multiplayer functionality to the franchise. Metro 2033: Legacy
Unlike games with flexible engines like Skyrim (which eventually received the Skyrim Together mod), the used for Metro 2033 was built specifically for highly scripted, atmospheric single-player immersion. metro 2033 coop mod
Here’s a short promotional/description piece for "Metro 2033 Co-op Mod": Several projects have surfaced over the years, aiming
* Divide and Conquer: Handle wave-based mutant encounters together. The Challenges of Modding Metro metro 2033 coop mod
While you cannot play the campaign in co-op, there is a modding scene surrounding Metro 2033 Redux that adds a multiplayer deathmatch component. This uses the engine's capabilities to create a PvP (Player vs Player) arena.