In Metamorphose, you are a goblin trapped in a dungeon experiment by a witch to determine the best traits among the varying different goblins and their abilities. Faced with goblins of three classes—Spike (brawler), Veil (ranged magic), and Wrath (warlock)—your goal is to evolve by consuming enemies and gaining their powers. Each class holds advantages and disadvantages over another, creating a hierarchy of strengths. As you kill goblins you are weak against, you evolve into a hybrid with new abilities. However, defeating goblins outside your evolution cycle causes you to lose powers. Strategically evolve, survive, and face off against a powerful boss at the end with all three class traits.

Spike is a brawler class which deals close range damage and has the ability to sprint. Veil is a magic class which deals ranged damage in bursts of projectiles based on where the player aims. Wrath is a warlock type magic user which charges up its shot and fires a homing high damage shot. Spike can sprint and get behind cover by the time wrath charges its shot while spike is an easy target for the burst firing of Veil. Similarly, Veil can be an easy target for Wrath due to the lack of sprinting ability while the fire rate of its burst fire makes it easy to kill Spike class goblins. When the player goblin kills a class it is at a disadvantage against, it "transcends by pushing beyond its limits" to evolve into a goblin having abilities of both classes. However, the player goblin loses its evolution by killing a goblin which was not a part of its evolution cycle. The player has different evolutions possible to discover. The player has to strategize the order of killing the remaining goblins to survive till the end. The loadout that the player ends up with at the end is the one they use to face a boss in the next room. The boss is a goblin which is higher up in the chain of experiments and possesses the abilities of all three classes.