The Long Beam is an upgrade for the Beam. The upgrade grants Samus the ability to shoot beams farther than the default distance and cause slightly more damage. Although it is very useful, in both games where it appears it can be skipped/ignored.
The Long Beam is present in Brinstar, in an item room with a unique corridor with blue brick platforms below the doors, as opposed to the grey of other Brinstar item rooms. The Chozo Statue holding it is blocked by a Red Door, requiring Samus to have Missiles in order to access it. Once collected, her beams gain no increase in offensive power, but are able to travel all the way across the screen. The beam is not strictly necessary for Samus's mission, however, and can be freely ignored (at the expense of having to rely on Missiles for long-range combat).
Metroid: Zero Mission
The Long Beam reappears in Brinstar and functions in more or less the same way - boosting the distance Samus's beams travel. However, it also affects the appearance of her beam and its strength - boosting it by half the Power Beam's normal strength. Unlike the original game, however, Samus is typically forced to collect it due to the Blue Door leading further into Brinstar being blocked by rocks requiring a long-ranged weapon to reach, though a hidden passage just above the Door allows her to bypass this and skip the Long Beam. Unlike the original game, however, Missiles aren't needed to access the Long Beam's room.
- The Long Beam has never appeared outside of Metroid and its remake, largely due to its function being combined with the normal Power Beam. Because of this, however, one could argue that the Long Beam is the one upgrade Samus has managed to keep throughout the entire Metroid series!
- Although the Long Beam doesn't appear in Super Metroid, a tile for the upgrade as it would appear in Samus's status screen is present in the game's data, indicating that at one point it was going to be collected.