Official co-op does not exist for Metro 2033 , and there is currently no functional, public "Co-op Mod" that allows you to play the full campaign with a friend.
The Metro 2033 Coop Mod is currently in "legacy maintenance." No new features are coming, but it remains playable for two patient survivors. metro 2033 coop mod
To understand why a co-op mod for Metro 2033 doesn't exist, you have to look under the hood at the X-Ray Engine (used by GSC Game World for S.T.A.L.K.E.R. and heavily modified by 4A Games for Metro). Official co-op does not exist for Metro 2033
However, the "Metro co-op" itch is currently being addressed through official developments and specific creative workarounds: Official Multiplayer: METRO 2039 To understand why a co-op mod for Metro
Garry's Mod/Men of War Maps: There are fan-made multiplayer maps for other games like Men of War: Assault Squad 2 that recreate Metro 2033 locations (e.g., "Metro 2 - Lost Station") for up to 4 players, focusing on combat rather than the full campaign story.
: The game's AI is designed to follow a single player. Adding a second player breaks most scripted events and stealth triggers. 🔮 The Future of Official Multiplayer In late 2020, developer confirmed that a future Metro title will feature a multiplayer component. Partnership : They are working with Saber Interactive to explore multiplayer possibilities. Philosophy
For over a decade, fans of the Metro series have asked one persistent question: "Can we play Metro 2033 in co-op?"