Metro: Last Light back in May 2011, the publisher stated that it would feature some kind of multiplayer. However, developer 4A Games announced today on the official blog that that was "probably a mistake".
According to the blog, "Throughout the development of Metro: Last Light a small, dedicated team had been working on a number of multiplayer prototypes. After E3, we decided to fold this multiplayer team back into the main group and focus 100% of the studio's resources on the single player campaign. As a result, Metro: Last Light will not ship with a multiplayer component."
The developer went on to say that it believed that a single-player campaign is "what the fanbase cares about the most."
When asked about adding multiplayer later, post-launch, 4A Games stated, "Right now we're 100% focused on the single player campaign and not thinking beyond that. We don't like throwing away work though, it's a project we could potentially return to after Metro: Last Light ships."