THQ is giving away the PC version of moody first-person shooter Metro 2033 for free.

All you have to do is like the Metro Facebook page. Once done, reveal the Steam code, load up the app and download the free copy of the game for Windows PC. The offer runs to 16th December 2012.

The deal follows Metro 2033's inclusion in the Humble THQ Bundle, which has generated payments of $4.5 million.

The embattled US publisher is raising cash as it battles to keep the business afloat following a crippling 12 months.

It's currently talking to a mystery financier in the hope that further investment will secure the release of 2013 games Metro: Last Light, Company of Heroes 2 and South Park: The Stick of Truth.