'Iron' in the Bible

Now the Lord was with Judah, and they took possession of the hill country; but they could not drive out the inhabitants of the valley because they had iron chariots.

The sons of Israel cried to the Lord; for he had nine hundred iron chariots, and he oppressed the sons of Israel severely for twenty years.

Sisera called together all his chariots, nine hundred iron chariots, and all the people who were with him, from Harosheth-hagoyim to the river Kishon.