Galactic Federation

The Galactic Federation is the governing body of the Metroid universe. They are supposedly a government formed to instill order in the galaxy, and are similar to most fictional sci-fi governing bodies in that they include members from many different races.

History
The original game stated that the Federation was formed in the year 2000, although that date is obviously non-canon and was retconned to be the year 2003 of the "cosmic calendar" (to differentiate it from the real year 2003). The formation of the Federation led to a race of violent creatures to form their own rebellious terrorist organization, and became known as the Space Pirates.

Marines
The Galactic Federation Marines are the fighting force of the Federation. Like most fictional space troops, they are depicted as rather inept at combat, and the Federation frequently hires bounty hunters, like Samus, to help them. The Marines wear a grey suit of armor with a visor and a gun of sorts on their right arms, making them vaguely resemble Samus. A dead Marine first appears in Super Metroid, and living ones first appear in Metroid Fusion. Actual 3D Marines first appear in Metroid Prime 2: Echoes.

Relationship with Samus
It is implied that at some point Samus may have worked in the Federation military. Eventually, she became a bounty hunter, and was first hired to kill Mother Brain and the Space Pirates on Zebes. When she succeeded, they began hiring her to do other tasks, such as investigate a distress beacon (Metroid Prime), find the source of a mysterious invitation (Metroid Prime Hunters), find out what happened to a missing contingent of Marines (Metroid Prime 2), eliminate all Metroids on SR388 (Metroid II: Return of Samus), and kill Mother Brain once again (Super Metroid). The Federation sends Samus on every mission she undertakes in the games with the exception of Metroid Fusion. Samus is considered an outlaw as of the end of Metroid Fusion.

Metroid breeding program
In Metroid Fusion, there are hints that the Federation may not be as benevolent as they appear. A conversation between Samus's ship computer and a Federation representative, that is witnesses by the player but not Samus, hints that the Federation may have set up Samus on the BSL station. Later on, Samus stumbles upon a Metroid breeding program run by the Federation, even though Samus was told to kill all Metroids. When Samus is finally able to defeat the X Parasite inhabiting her suit (the SA-X), the Federation tells her not to kill it and instead allow the Federation to capture it. Knowing the Federation would be wiped out if they attempted to fight it, Samus disobeys orders and kills it herself. Samus is then considered an outlaw by the the Federation. As there has been no game, chronologically, that takes place after Fusion, Samus's status with the Federation is currently unknown.