Deep Silver and 4A Games confirmed via press release that a Mac version of Metro: Last Light will be released on the App Store and Steam on 10 September, 2013. They also announced that a Linux version is currently in development, scheduled for release later this year (2013).
“The Mac and Linux versions of Metro: Last Light are further testimony to the power and flexibility of the 4A Engine,” said Oles Shishkovstov, Chief Technical Officer at 4A Games. “Development was handled in house by 4A games, and we are very happy with the results. We hope that Mac & Linux gamers will appreciate our efforts to create the best possible version for their machines.”
Metro: Last Light will support Steam Play, which will allow current owners of the PC version to download and play the game on their Mac and/or Linux computers.
The Mac and Linux versions of Last Light will receive the same DLC content as the PC and console versions of the game. The Faction Pack and Tower Pack will be available on release for the Mac.
Source: AIE/Deep Silver Press Release