Valve has taken the wraps off a new section on Steam reserved for games following the 'Free-to-play' model. Although the company has hosted promotional free-to-play weekends before, with games such as Call of Duty: Black Ops or Team Fortress 2 for example, this marks the first time Steam will offer games that are free to download and keep, supported solely by micro-transactions.

A total of five free-to-play games are launching on Steam this week: Spiral Knights, Forsaken Worlds, Champions Online: Free for All, Global Agenda: Free Agent and Alliance of Valiant Arms (AVA). The company will be highlighting each game and giving away special in-game content through a "F2P game of the day" feature on Steam, starting with Spiral Knights on Wednesday the 15th and concluding with AVA on Sunday the 19th.

"The introduction of Free to Play games is another example of the constant evolution of Steam," said Jason Holtman, director of business development at Valve. "Free to play games offer new game genres and game experiences for customers while offering developers and publishers new revenue opportunities and the ability to reach customers in areas of the world where the traditional packaged goods model is less popular than F2P."

As you'd expect, there are no subscription fees or upfront payments. Of course, after getting a first taste, the idea is that you'll be encouraged to buy virtual items to enhance gameplay in some fashion or unlock certain levels of a game. All transactions will be handled by Valve's Steam Wallet back end, which is already used widely by Team Fortress 2 players.