There are three game modes available in Grey Goo.
The Single Player Campaign tells the story of Grey Goo, and switches between the three standard factions" Beta, Humans, and Goo, in that order. Each faction has five missions attached to it - with the exception of The Herald of Silence, which is a sixth Goo mission added in a DLC.
The Emergence DLC Campaign takes place shortly after the Human campaign ends, and follows the story of the Valiant AI "Singleton".
There is also a single player Skirmish Mode where you can play as any of the four factions with up to three AI teammates or enemies. Maps support either two or four players. The three available victory conditions are:
- Standard: Destroy all enemy production buildings, refineries, headquarters, or mother goo
- Annihilation: Destroy all units and structures
- Destroy HQ: Destroy the enemy HQ once to win.
The multiplayer consists of ranked and unranked multiplayer, very few players run ranked matches anymore - multiplayer matches are best organized by Discord servers.