Sector 5 (ARC) is the arctic sector in Metroid Fusion on the BSL research station. This section of the space station is meant to simulate icy sub-zero environments, such as arctic or tundra. Without the Varia Suit, it would be impossible for Samus to explore this sector, due to her newly-gained vulnerability to cold. Samus unlocks the Yellow Hatches here. Both Ice Missiles and Power Bombs are acquired here, by means of downloading. After the Power Bomb, Samus encounters the SA-X, nearly chasing Samus through half of the Sector. She later faces Nightmare here, but this is only after he has broken free, destroyed nearly all of the sector, and melted most of the ice. Samus is assigned to neutralize it due to the threat it presents to the rest of the station. After its defeat, Samus recovers the Gravity Suit.
- Blue X
- False Energy Tank
- Mermen Pirate
- X Parasite
- This Sector has to be visited the most out of all six; approximately three times. Once for an initial visit, once to go back to the Data Room to gain Power Bombs, and finally, to deal with Nightmare.
- This is the only Sector that contains Yellow Hatches. This may be extra security for Nightmare. It could also be attributed to the fact that this is the last Sector that Samus goes to explore (when the game is introducing the six areas).
- "Facing a Huge Reaction" (as named on the Metroid Prime & Fusion Original Soundtracks tracklist) plays in this sector a total of three times: on her first visit to Sector 5 until she reaches the first frozen room, after exploring the Habitation Deck and returning here to use the Data Room, and after defeating Nightmare. The latter instance is the last time the theme is heard in the game, and it continues until Samus reaches the aquatic portion of Sector 4.
"This sector is used to research creatures living in extremely cold habitats."
"The arctic sector is filled with organisms that thrive in sub-zero temperatures."