§fPress and hold Use to charge the Arm Cannon, then release Use to fire.

[C]§e§lSamus's Notes:
§fThe Charge Beam has a limited 'tractor beam' capacity. Use it to pull item refills to you.
§fThe Charge Beam increases the performance of each Arm Cannon mode.
§fThere are Charge Combo enhancements that can be obtained. They use the Charge Beam and the Missile Launcher in tandem to fire more effective blasts.
§fTo use a Charge Combo, fully charge the Arm Cannon, then press the missile fire button.