A long time ago, there was a planet named Machina where a race of sentient machines, or Metal Cardbots, resided. One day, the planet suddenly explodes, forcing its inhabitants to live on Earth. To not attract attention, the Cardbots disguise themselves as everyday vehicles. In the present day, Jun, an elementary school kid who loves BMX, accidentally discovers the Metal Breath, a wrist gadget that allows him to capture and power up the Cardbots with different abilities.