Iron

Tubal-Cain is the first-mentioned worker in iron (Gen. 4:22).
The Egyptians wrought it at Sinai before the Exodus. David
prepared it in great abundance for the temple (1 Chr. 22:3:
29:7). The merchants of Dan and Javan brought it to the market
of Tyre (Ezek. 27:19). Various instruments are mentioned as made
of iron (Deut. 27:5; 19:5; Josh. 17:16, 18; 1 Sam. 17:7; 2 Sam.
12:31; 2 Kings 6:5, 6; 1 Chr. 22:3; Isa. 10:34).

Figuratively, a yoke of iron (Deut. 28:48) denotes hard
service; a rod of iron (Ps. 2:9), a stern government; a pillar
of iron (Jer. 1:18), a strong support; a furnace of iron (Deut.
4:20), severe labour; a bar of iron (Job 40:18), strength;
fetters of iron (Ps. 107:10), affliction; giving silver for iron
(Isa. 60:17), prosperity.