On a far away planet, three races fight for control of the few landmasses available: the marooned Meccs, who specialize in firearms and other things that go boom, the mystical and cold-blooded Reapers, who were the original inhabitants of the planet, but were forced to live in the sea by Kabuto, the third character; a truly gigantic monster with a ravenous appetite and a fondness for performing wrestling maneuvers on those the size of his hand.
You can control any of these races (although in the single player mode, you have to progress through the storylines of the Meccs and Reapers first) in their bid to be the dominant species. Each species various in the way they play the game and have vastly different types of attacks available to them.
Giants is a action/real-time-strategy game that emphasizes action. While there is base-building and resource management for most of the races, it is a done through a simple to control interface and one or two keystrokes. The majority of the game will be spent in a third person view (first person mode is available) jet-packing/warping/leaping about the well rendered 3D landscape. Single player sessions consist of missions with specific goals, such as resucing Smarties or recovering lost items. Multiplayer options include standard deathmatch, capture the Smartie (flag), the above with basebuilding as an option.
Other creatures also inhabit the islands. From the meek Smarties (who are employed to build your bases or eaten as a primary source of protein, depending on your species), to the cow-like vimps to the deadly rippers, the fauna of the planet will either try to kill you or avoid being killed/eaten/captured. While not so energetic, the floral of the islands can be crushed, knocked over, or burned in careless combat (or by Kabuto not paying attention).