Shall iron.

Jeremiah 1:18, 19
Now behold, this day I have made you a fortified city, an iron pillar, and bronze walls against the whole land--against the kings of Judah, its officials, its priests, and the people of the land. . . .

Jeremiah 21:4, 5
This is what the LORD, the God of Israel, says: I will turn against you the weapons of war in your hands, with which you are fighting the king of Babylon and the Chaldeans who besiege you outside the wall, and I will assemble their forces in the center of this city. . . .

Job 40:9
Do you have an arm like God's? Can you thunder with a voice like His?

Isaiah 45:9
Woe to him who quarrels with his Maker--one clay pot among many. Does the clay ask the potter, 'What are you making?' Does your work say, 'He has no hands'?

Habakkuk 1:5-10
Look at the nations and observe--be utterly astounded! For I am doing a work in your days that you would never believe even if you were told. . . .