Plasma Beam

The Plasma Beam appears in all of the Metroid games except for the original and Metroid Prime 2: Echoes. In most games, it allows you shoot beams that pass through enemies. However, in Metroid Prime, it fires searing rays of plasma at an accelerated pace that incinerates most enemies.

In the Metroid Prime series
In Metroid Prime the Plasma Beam's Charge Combo, the Flamethrower, was a continuous Charge Combo,a stream of flame with an exceedingly short range, useful for killing Plasma Troopers and cold-based enemies, such as Sheegoth. The Plasma Beam's color scheme in Prime was red, and it represented the "element" of fire. The Plasma Beam was the second to last beam in Metroid Prime, and as such, besides the Phazon Beam it is perhaps the most powerful beam weapon, besides the hyper beam from Super Metroid.

In Metroid Prime 3: Corruption the Plasma Beam is acquired after defeating the hunter Ghor. The beam was no longer short ranged and the rate of fire remained the same as the Power Beam (all beam weapons were stacked upgrades in Metroid Prime 3). It retains its ability to ignite enemies and melt objects, however it's gun "position" was altered. No longer is the gun extended forwards, instead, it takes after the Ice Beam from Metroid Prime by being slightly elevated upwards and it also takes the shape of the Dark beam from Metroid Prime 2 Echoes. Newly however to the Plasma Beam, in Corruption, is it's ability to repair damaged cables with a welding-type attachment.

In Other Games
In Metroid: Zero Mission, the Plasma Beam was gained as an unknown item and could not be used until the Power Suit was regained in Chozodia.

In Super Metroid, the Plasma Beam was incompatible with the Spazer Beam. If both were simultaneously selected with a variety of other factors, the game would glitch with results such as the Murder Beam.

Interestingly, in Metroid Fusion, the Plasma Beam also looked much like the Spazer; it split into three long, green lines, like the version of the Spazer from Super Metroid. This may or may not have been caused by the previously-gained Wide Beam.

When charged up, it has the potential to destroy many enemies with ease. This was very effective against most enemies.