I know this sounds like a stupid question, but I'm talking about what ANIMAL it's based on. (ik faries and flowers aren't animals but most Pokemon are animals) Is it a frog, is it a bug, is it a baked potato, FOR ARCEUS' SAKE WHAT IS THIS THING.
Heatran is a blob of magma turned dragon.
According to legends, Heatran was said to have been created from the magma hidden beneath Mount Coronet. The body of Heatran is said to hold many unsolved mysteries.
Heatran may be based on volcanic remains. Its Steel typing may reference how the Earth's inner core is made of solid metal under immense pressure. It may be also based on a personification of magma. In the ancient mythologies of most cultures, the eruptions of volcanoes were explained by the presence of a fire monster living within it, often a dragon.
source
