Metamagic, as its name implies, is magic used to alter magic. At a very basic level, it can change structures of spells. Class Skills learned as a Mage (e.g., Focus Spell, Empower Spell) are types of metamagic. On a higher level, one can call the magical foundations of the world a “spell,” and metamagic can change the structure of the world. The bizarre flecks, for example, have this sort of metamagical effect on the world.