Metro 2033 domains listed on THQ’s nameservers and a listing on The CDR suggest the publisher may be giving away the game for free as a Metro: Last Light pre-order incentive.
Fusible dug up the domains GetMetro2033free.com and FreeMetroGame.com through WHOIS, and while the sites are listed private through Go Daddy’s WHOIS service, domains show up in THQ’s nameservers list.
THQ has not made any announcements on the matter, but with Metro: Last Light slated for a March release, its possible the firm could be handing out its predecessor as a pre-order incentive to help pad the sequel's sales.
More proof of this (thanks, ballz) is posted over on The CDR, which is a record of "data that describes every Steam game and subscription provided by Valve for the Steam service."
On CDR, alisting for "Metro 2033 December Giveaway" was posted on November 10, and the content description under "Billing Type" lists the title as "ProofOfPrepurchaseOnly."
Sounds likely that the game will be handed out as a pre-order incentive for Metro: Last Light stating in December, which considering Last Light is slated for March, the listing makes perfect sense.
We'll send THQ a mail and ask at any rate.