'Iron' in the Bible

And passing through the first ward and the second, they came to the iron gate leading into the city. This opened to them of itself; and, going out, they passed on through one of the streets, and then suddenly the angel left him.

through the hypocrisy of men who teach falsely and have their own consciences seared as with a hot iron;

And he shall be their shepherd, ruling them with a rod of iron, just as earthenware jars are broken to pieces; and his power over them shall be like that which I Myself have received from My Father;

She gave birth to a son--a male child, destined before long to rule all nations with an iron scepter. But her child was caught up to God and His throne,

From His mouth there comes a sharp sword with which He will smite the nations; and He will Himself be their Shepherd, ruling them with a scepter of iron; and it is His work to tread the winepress of the fierce anger of God, the Ruler of all.