Revelation 2:27

2:27 he will rule them with an iron rod

and like clay jars he will break them to pieces,

Revelation 9:9

9:9 They had breastplates like iron breastplates, and the sound of their wings was like the noise of many horse-drawn chariots charging into battle.

Revelation 12:5

12:5 So the woman gave birth to a son, a male child, who is going to rule over all the nations with an iron rod. Her child was suddenly caught up to God and to his throne,

Revelation 19:15

19:15 From his mouth extends a sharp sword, so that with it he can strike the nations. He will rule them with an iron rod, and he stomps the winepress of the furious wrath of God, the All-Powerful.