|This article is written from the Real Life point of view|
The Metroid Battle Theme originally appeared in Metroid Prime as the battle theme heard when fighting Chozo Ghost(s), an Elite Pirate, or escaping Metroids. On the Metroid Prime & Fusion Original Soundtracks, it was titled VS Chozo Ghost (VS.チョウゾゴースト).
The Metroid Battle Theme returned in Metroid Prime 3: Corruption, where it was heard only once. If Samus removed the Energy Cell in Metroid Processing on the Pirate Homeworld, the shields holding numerous Phazon Metroids back would shut down, and allow the Metroids to escape. The theme is only heard during the first battle, and on further visits to the room the theme does not play at all.
Corruption's Soundtrack Gallery had the song available for purchase. However, this, along with the Bryyo Thorn Jungle theme, was removed in Metroid Prime Trilogy and replaced with the Berserker Lord and Aurora Unit 313 themes. On the UK Corruption website, it is known as Track_9 in the music player.
It can be heard here: .