'Iron' in the Bible

Am I as strong as a rock? Am I some kind of iron man?

That they were graven with an iron pen and lead in the rock for ever!

He shall flee from the iron weapon, and the bow of steel shall strike him through.

Iron is taken out of the earth, and brass is molten out of the stone.

His bones are as strong pieces of brass; his bones are like bars of iron.

Who has ever taken off his outer skin? who may come inside his inner coat of iron?

The sword may come near him but is not able to go through him; the spear, or the arrow, or the sharp-pointed iron.

He esteemeth iron as straw, and brass as rotten wood.