Blacksmith in Ancient Greece (ca. 530 BC)
On the left there's an Ancient Greek vase showing a blacksmith heating up iron while a younger boy works the bellows to blow the fire hot enough. Below, there's a video of a blacksmith making something out of iron. First he heats up the metal so it will get softer, and then he beats it into shape with a hammer.
Because iron is so hard to make, nobody used iron before about 1500 BC. Then the Hittites in West Asia did learn how to use it. But they quickly saw that iron weapons were better than bronze ones, and so they decided not to tell anybody else how to make iron. The Hittites kept the secret of making iron for about 400 years, until about 1100 BC, but when the Dark Ages came to West Asia, the Hittite empire fell apart anyway, and the secret of making iron got out to other people.
After the Dark Ages, therefore, all the Mediterranean people started to use iron: the Greeks, the Egyptians, the Kushites, the Jews, the Philistines, the Romans, the Carthaginians, and the Assyrians. From about 1000 BC to the present day, iron has been the most used metal.
When the Aryans invaded India, around 800 BC, they brought the knowledge of how to make iron with them there. People who lived in China learned how to make iron by around 700 or 600 BC, during the Eastern Chou dynasty.
By about 300 AD, people in West Africa and East Africa had also learned the secrets of making iron. Some people think they learned how from the Egyptians; other people think the Africans figured it out on their own.
Each culture brought their own new ideas to the use of iron. In India, for instance, by the 1000s AD architects were making iron beams to hold up the roofs of big temples.