Nintendo has announced how amiibo functionality in the upcoming Metroid: Samus Returns will work. Revealed alongside the remastering of Metroid II was a duo of Metroid-series amiibo, and they along with two existing Samus Aran figures will unlock exclusive features, functions, and bonuses.

From the 2-pack pictured on top, the Samus figure will unlock the Elon Reserve Tank (a special ability recovery)
and a Metroid II Art Gallery. The Metroid amiibo unlocks the Metroid Marker that tells you the location of nearby Metroids, and a Fusion Difficulty Mode.

For the preexisting Metroid-related amiibo from the Super Smash Bros. line, that Samus Aran figure unlocks a Missile Reserve Tank and a Concept Art Gallery, while the Zero Suit Samus will unlock the Energy Reserve Tank and a Sound Test. For all the above, the sound test, art galleries, and Fusion difficulty mode are also unlocked after completing the game once.

Metroid: Samus Returns and the Metroid amiibo 2-pack both launch on September 15th, following a well-received reveal at E3. All the above features are locked behind these amiibo with no announced way to access them in-game alone, so plan accordingly.