Cybertron

What is Cybertron?
It's an entirely metallic planet composed of various ores (including cybertronium) and energon—the substance necessary for all Transformer systems to operate. It's much larger than Earth.
Some features of the planet:
Atmosphere. Surrounded by an oxygen "capsule" similar in composition to Earth's. Transformers don't require oxygen to breathe, but humans can survive on Cybertron without a spacesuit.
Terrain. The surface is uneven, covered with metal plates, faults, mountains, and deserts (one of the largest is the "Sea of ​​Rust"). In the depths lies a system of tunnels and mechanisms.
Who lives on Cybertron?
The main population of the planet are transformers (Cybertronians), powerful robots capable of transforming into various vehicles and equipment. The height of most transformers varies between 3.5 and 11 meters.

Besides them, other creatures inhabit Cybertron:
Mini-cons are miniature robots (about the size of a human child) who are very gifted and hardworking.
Semi-intelligent creatures. Dangerous creatures such as Desert Hunters (relatives of Scorponok), Insecticons, and Predacons lurk in the remote regions of Cybertron.
Robo-fauna. The planet is home to mechanical birds, fish, and other creatures. Some are dangerous: for example, the computer center is home to bats, energy-feeding leeches, and spiky rat-lizards whose teeth can bite through a Transformer's body.

There are more transformers on this planet than anyone else.