'Iron' in the Bible

As for all the hills that used to be cultivated with a hoe, you won't go there, because you'll fear iron briars and thorns. Nevertheless, those hills will be reserved as a pasture where cattle will feed and where sheep will graze."

"I myself will go before you, and he will make the mountains level; I'll shatter bronze doors and cut through iron bars.

Because I knew that you are obstinate, and because your neck is an iron sinew, and your forehead is bronze,

"Instead of bronze, I'll bring gold, and instead of iron, I'll bring silver; instead of wood, bronze, and instead of stones, iron. I'll appoint peace as your supervisor and righteousness as your taskmaster.