break them. rule, or govern them. So Septuagint, Syriac, and Vulgate.
rod. sceptre.
iron. Put by Figure of speech Metonymy (of Adjunct), for unbending authority.
Related Commentaries of Psalms 2:9
Psalms 2:9
9 Thou shalt break them with a rod of iron; thou shalt dash them in pieces like a potter's vessel.