The Milky Way galaxy is explorable once you get control of the SSV Normandy and you gain access to the Galaxy Map. The Galaxy Map is located in the center of the Normandy's command deck. Their are four levels of the map. The four levels are Galaxy, Cluster, System and Planetary. Through this map you will be able to explore countless Planets, Space stations and Asteroid Fields that have various objectives.

Planets are massive celestial bodies that orbit a star or stellar remnant. They are of many different sizes and compositions. Planets may have natural satellites (moons) and may or may not be inhabited. Some planets in Mass Effect can only be scanned from space and not landed upon. Travel from planet to planet requires use of the Galaxy Map.