METAL SLUG 3 is a shoot-em-up video game and a continuation of the first two parts of the franchise. The main character managed to suppress the uprising of General Morden, who was trying to take over the planet. Peace was restored on the continents, but once again Morden returned to power and tried to make new difficulties for the inhabitants. The government, having learned about the conspiracy in advance, managed to prevent him from making another attempt to take over the world.

Marco Rossi and Tarma Rowing are members of the Sapsan squad, and they managed to destroy the general’s forces the previous time. After a short absence, they began to assemble the team again. The main characters will have to suppress the riots one by one. Previously, they chose to hide their own existence and not reveal to the world who exactly saved the planet. This can work to the characters' advantage and help them with their next task. The player will become a participant in fierce battles and will fight with the rebellious system.

The basic gameplay remains the same as in previous Metal Slug titles. The main innovation is the ability to complete missions in several ways, each of which is unique and presents different dangers. All roads will lead to a single boss at the end. In addition to the fact that you can turn into a mummy, your ward can become a zombie if an infectious liquid gets on him. The project has added a variety of vehicles for movement and battles. A jetpack, air and space plane also appeared.