Metal Saga is a free-form RPG with only the barest of storyline to follow. The player's goal is mainly to explore, find new cities, fight new monsters, and salvage new tanks. Posted bounties on especially dangerous criminals will clue the player into to events and boss fights they can find.
At the start of the game the main character can choose from being a hunter or a mechanic, but it's only possible to play as a hunter. The hunter is a Jack-of-Trades in the Metal Saga world, skilled at combat and a gun-for-hire to anyone who can pay the price. His skills tend towards status related buffing and fleeing/avoiding combat. He can also call down an orbital laser strike. He can equip almost every weapon.
Both of the Hunter's childhood friends are mechanics, and one of them will take up the party's second character slot. The mechanic provides the vital service of quick in-combat fixes to tanks. They can repair broken parts, restore armor plates, and even restore a shut-down vehicle. They can equip wrenches and some guns.
Even more than the hunter these characters focus on offense. The Hunter will have a choice of two characters for this slot, Rashid and Charlene. Rashid can equip swords, while Charlene uses heavy duty firearms. Their skills focus on all out attack.
The party's final member is one of four dogs: Shiba, Tosa Inu, Boston Terrier, and St. Bernard. Each dog has a different skillset, but they mostly use the same weapons (missiles and laser canons strapped to their backs). Unlike the other three party members the dog can not be controlled, and will act (or flee) based on how friendly it is (represented in-game by the "shiny coat" stat).
Every vehicle in Metal Saga has three weapon slot types: Main Gun, Sub Gun, and SE. The Main Gun is the most powerful weapon a tank has, but it has limited ammunition and takes time to reload. The Sub Gun is a faster, less powerful alternative that will not run out of ammo. The SE weapon can have a variety of effects, such as an electrical net that hits all enemies or an AA gun. It also has limited ammunition that must be repurchased.
Instead of "hit points" tanks have Armor Tiles. Armor Tiles have to be repurchased if depleted, but a Tank at zero armor is not destroyed. Instead every subsequent attack to the tank will hit one of its parts: the chassis, engine, computer, or equipped weapons. If the attack deals more damage than the part's durability the part will be broken, reducing the tank's effectiveness. Every part has a weight, and parts attached to a tank must be below its maximum weight limit, with all remaining limit available to be used by armor tiles. Tanks are faster when not weighed down, however, so a lightly equipped tank with no armor tiles would act faster than the same tank filled with tiles.
Tanks can be painted with a variety of paint jobs, or a custom paint job can be created using an in-game painting application.
Every town has a hunter station that can be visited to check and redeem local bounties. In addition to a small bounty placed on a particular type of randomly encountered enemy, there are also much larger bounties placed on unique enemies. These could be enemies found wandering the map, bosses located at the end of dungeons, or special characters who appear during events.