Charge Beam
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.
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 the 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.