In advance of Metro: Last Light's debut early next year, THQ has made the original Metro 2033 free through a new Facebook promotion. Beginning today and running through December 16, gamers can score a PC copy of the 2010 shooter by "Liking" the official Metro Facebook page.

Download codes are redeemable through Steam. The Metro 2033 promotion is open to legal residents of the United States and the District of Columbia who are 17 or older. The offer is also available for United Kingdom residents.

Metro 2033 was released for the PC and Xbox 360 during March 2010 to generally positive reviews. A film based on Dmitry Glukhovsky's science fiction novel, which was the source material for Metro 2033, is also in the works.

As for its sequel, Metro: Last Light, that game was recently delayed to March 2013 and is currently in development at 4A Games for the Xbox 360, PlayStation 3, and PC. Competitive multiplayer was at one time planned for the game, but has since been scrapped.

For more on Metro: Last Light, check out GameSpot's previous coverage.