Daniel 7:19
Then I would know the truth of the fourth beast, which was diverse from all the others, exceedingly dreadful, whose teeth were of iron, and its nails of bronze; which devoured, broke in pieces, and stamped the residue with its feet;
Daniel 7:7
After this I saw in the night visions, and behold a fourth beast, dreadful and terrible, and strong exceedingly; and it had great iron teeth: it devoured and broke in pieces, and stamped the residue with its feet: and it was diverse from all the beasts that were before it; and it had ten horns.
Daniel 2:40-43
And the fourth kingdom shall be strong as iron: since iron breaks in pieces and subdues all things: and as iron that breaks all these, shall it break in pieces and bruise.