Metroid Prime/Chozo Artifacts

You now have every upgrade in the game, but in order to get to the final area you need to collect all 12 of the Chozo Artifact. They aren't actually useful until this point in the game, so you can get them as they become available or wait and get them all at once according to your preference.

Artifact of Truth
You can collect this artifact after getting the Missile Launcher. Go to the Artifact Temple in the Tallon Overworld. (See the Missile Launcher page for directions.) The artifact is located under the central statue. Once you have this artifact you can get clues to the locations of some of the remaining ones by scanning the other statues. You'll be able to scan all the statues after getting more artifacts.