Overview

Metroid Zero Mission takes place on the planet Zebes, which is divided into the following major area:

 Brinstar
 Crateria
 Norfair
 Kraid (Area)
 Ridley (Area)
 Tourian
 Chozodia + Mother Ship

The entire map of the game:

For the full size version of the above image click here

In your playthrough, you will explore all of these areas to some extent. You will start in Brinstar and depending on the category and your route, you first goal will be the Kraid (Area) or to the Ridley (Area) to beat the namesake bosses to open up the gate in Brinstar that will let you go into Tourian to beat Mother Brain. This first half of the game allows for varying routes and are most of the time about your own personal preference, because timing-wise they are quite similiar.

After you have beaten Mother Brain and escaped the planet, your ship will be shot down and the post-game section will start. It starts with a stealth section (commonly referred to as "Suitless"). No matter what category you're running, Suitless is always the same. The exception to this is Hard Mode, which adds more search lights to the search light rooms. After defeating Charlie you will always receive the Gravity Suit, Plasma Beam and Space Jump and the rest of the game opens up with the only remaining goal being to defeat Mecha Ridley to finish the game.