Metro: Last Light will come bundled with Steam Machine prototypes
Steam Machines are coming soon. Very soon. In fact, they're supposed to come as soon as early 2014. Even sooner than that, however, Valve will send out a prototype of its own design to 300 randomly-selected users for beta testing and it announced a game to come bundled with those prototypes for SteamOS testing.
4A's post-apocalyptic survival horror gem, Metro: Last Light, will be that game. After a May release date on Windows in May of this year, the game landed on Linux and Mac earlier this week. Considering that Linux is the basis for SteamOS, the operating system that Valve plans to release early next year, it was already at least partially primed to work on a Steam Machine.
The entire catalog of Linux-compatible Steam games should be available to play on SteamOS when it launches next year. Although that currently includes just around 200 games, there will be no shortage of games to play if you switch to the OS. You can always manually add non-Steam games into your Steam library and SteamOS will be able to play non-Linux games. But with Metro and the recently-announced Linux version of Total War: Rome II that will also be compatible with the Steam Controller, we can count two more relatively high profile additions to the Linux slate.