'Iron' in the Bible

And the LORD was with Judah, and he took possession of the hill country, but he could not drive out the inhabitants of the plain, because they had chariots of iron.

Then the people of Israel cried to the LORD for help; for he had nine hundred chariots of iron, and oppressed the people of Israel cruelly for twenty years.

Sis'era called out all his chariots, nine hundred chariots of iron, and all the men who were with him, from Haro'sheth-ha-goiim to the river Kishon.