How To Meter Burn
Meter Burning can be done in the middle of performing a Special Move in a battle. Pressing the back right button (R2 on PS3 and RT on Xbox 360) during the move will meter burn it.
Meter Burns are unique for each move. In most cases, they increase the damage given by the move. However, they often also set up extra combo opportunities and increase the move's range.
Meter Burn appear as a black vortex at the character who use it. Indicating it's Meter Burn.