In the Wii Version of Godzilla Unleashed, monsters can achieve a form called Critical Mass which applies a magma-like texture across their body. This is true for all monsters except Godzilla 90's,
RGZE70 - Godzilla Unleashed
Amazon.com: Godzilla Unleashed - Nintendo Wii: Artist Not Provided: Video Games
Godzilla Unleashed - All Characters / Monsters - YouTube