In early days, early humans would have found the metal in the form of volcano lava. After getting cool, ores in lava would have been converted to metal. But they could not make it on their own. But with time they would have observed that the jungle fire usually left many burnt products after it. They would have found that some of the partially melted stones converted to solid metals as cool residuals. This gave them the idea of extracting metals from such ores.
Early human making tool image
Now they were aware of how to extract metals from the hard stones. They started melting such stones in fire and began to make tools for farming also. Most probably, this way, they would have made plough for the first time that had to be used for softening the soil for farming.
This made the early humans the real farmer and they made their farms near river banks and started living in joint family. As he was not able to do all farming works alone so they divided their works too. This was the seed of a civilized early human.