The Charge Beam is an item in the Prime games that allows Samus to shoot a charged shot after holding the A button for a certain amount of time. In Metroid Prime, the Charge Beam is a physical item that can be collected in Watery Hall. In Metroid Prime 2: Echoes and Metroid Prime 3: Corruption, the Charge Beam is already equipped by default and cannot be removed by normal means. However, Charge Beam can be made into a collectable item in Randomizers in order to bring forth more variety.
The game keeps track of how fully charged your shot is, up to an upper limit. This can be used by the game to change how much damage the charged shot deals. For example, in Echoes, the Light Beam shoots a different amount of light rays depending on how charged the shot was upon releasing the A button. A minimally charged Light Beam shot will fire 5 light rays for a maximum of 50 damage, whereas a maximally charged Light Beam shot will fire 10 rays for a maximum of 100 damage.
Charge Beam is also required in order for beam combos to be usable, including the Super Missiles.
Expanded Splash Damage
In Prime 1, all beams have the ability to activate doors without needing to touch them directly, provided they are within a certain range. As shown below, this range is increased for every beam in the game. This makes opening doors with Charge even more lenient than with uncharged beam shots.
Usage in Speedruns
While Charge Beam isn't a required item for beating Prime 1, runners will still take the time to get this item, despite that getting the item is a bit of a detour in the route. The reason for this is mainly because this lost time is made up for during the Chozo Ghosts fight in Sunchamber. If the player skips Charge Beam and takes on this fight, not only does it require intensive mashing which can be hard to do, but it takes far longer to kill the Ghosts, losing all of the time that skipping Charge would have otherwise saved. Therefore, all speedruns will pick up Charge as soon as possible to save time on this fight.
Scan Visor Charge Storage
Missile Firing Optimization
When firing a missile in Ice Beam (TODO: Check other beams), charging after the missile is launched will cancel out part of the post-missile-launch animation on Samus' Arm Cannon, shortening the cooldown length before the Arm Cannon is usable again. TODO: Video