Peter Pett's Commentary on the Bible
Ezekiel 22:17,18
The House of Israel Who Are Full of Impurity.
‘And the word of Yahweh came to me saying, “Son of man, the house of Israel is become dross to me, all of them are brass and tin and iron and lead in the midst of the furnace. They are the dross of silver.”
In this second oracle ‘the house of Israel' are described as dross, the impurities that are left when the silver is purified. And while the main idea is of ‘the house of Israel' in Jerusalem and Judah, there is an implication in the use of the term that it also includes much of Israel far and wide. They are impure and unworthy.
We may here see it as meaning that brass, tin, iron and lead, which were of a lesser value in themselves, were to silver as comparative dross, for Ezekiel is not speaking as a metallurgist. To him compared with silver they are nothing. They are equal to the dross of silver. On the other hand some see it as meaning that Israel are as the dross of all these impure metals when they are refined.
It is important to see that, unlike other Old Testament passages, the idea here is not that they will be refined, but that they will be destroyed as worthless dross.