TRAIT - Metamagic
Actions with the metamagic trait, usually from metamagic feats, tweak the properties of your spells. You must use a metamagic action directly before Casting The Spell you want to alter. If you use any action (including free actions and reactions) other than Cast A Spell directly after, you waste the benefits of the metamagic action. Any additional effects added by a metamagic action are part of the spell's effect, not of the metamagic action itself.
Source: Core Rulebook pg. 634 2.0