Metro: Last Light has been updated for Macs today. The game supports Steamplay, so if you've purchased the Windows version already you can access the Mac version for free.
The Mac port of Metro: Last Light will make its way to the App store soon, publisher Deep Silver says. All DLC and the Season Pass will be available to Mac users, while a Linux port is due sometime later this year.
Metro: Last Light is set a year after the events of 4A Games' Metro 2033, based on the novel of the same name. Metro: Last Light follows humanity's struggle to survive while inhabiting the underground subway systems of Russia following an apocalyptic nuclear war. It's a game our review said "truly excels at pacing and direction, even while it dabbles with verbose characters and an ambiguous supernatural element."