Why do all metallurgy gods have a limp?
Hephaestos, an ancient Greek god of metallurgy and blacksmithing, was born ugly and his mother Hera threw him from the Olympus after which he had started limping. He and a Roman god of metallurgy, Vulcan, had both made weapons for the gods.

In ancient Egypt Ptah was the god of craftsmen and metallurgy. He was often depicted as a dwarf which was a custom in the Old Kingdom because dwarfs were seen as experts in goldsmithing and metallurgy. The same thing which we can see in Europe, too.

So, why do all the metallurgy gods have a limp? Why are they depicted as dwarfs?
It's because in the Bronze Age metallurgy workers, blacksmiths, got sick with arsenic poisoning from the fumes. The consequence of that is limping and above average libido and sexual power.

His role is the similiar to one of a shaman, sorcerer. They often have their special drinks which fuels them from the inside - a fire or a spark inside of them. Blacksmiths control the fire and sparks in their weapon forging. But blacksmiths are also seen as outcasts...

...and they are often depicted as strange men who live in the mountains. It's because their knowledge is sacred, it is the spark of connection which is held in secret. This is especially seen with Kouretes who are also metal workers who hold their knowledge in secret...

...another interesting aspect of them is their dancing in front of caves while clashing their weapons. Knowledge of metallurgy was sacred and it was seen as divine as it holds very obvious chthonical characteristics. Blacksmith, who often were limping, were seen as wise...

...they were the ones in touch with the spark of life and ancestral spark. That is why they are depicted as the ones who "come down from a mountain" - because they are connected to their forebears and their spark. This is very closely related to dwarfs who do the same in stories.

The term "coming down from a mountain" is how people describe wolves (representations of forebears). So the blacksmiths were seen as in contact with the spirit world and forebears, in control of the fire and the ancestral spark. Their role is important, like the one of a shaman.

Similiar to them are the potters who work with clay. Clay is extracted from the earth, metals are extracted from the mines/underground. They both work with fire, they are the creators so they have to be connected to the underworld.

Their connection with nature was pure and symbological. They held respect for the nature and saw themselves as a part of it. Things from everyday life were entwined with the myths and gods so they cannot be separated- the pattern has to fit in every aspect of their lives.