Interesting evidence of the essential link between Yahweh and copper metallurgy is provided by the story of the first 'encounter' between Moses and Yahweh on Mt Horeb, near the 'burning bush' (Exod. 3), where it is related that Moses is involved in the mission to deliver the sons of Israel from Egyptian tyranny. It is also stressed that Moses had to perform a 'prodigy' in order to demonstrate that he acts in the name of Yahweh (Exod. 4.5). This prodigy is depicted as the reversible transformation of a matteh into a nahash (Exod. 4.2-5).
The term matteh is generally understood as designating a wood-made staff, but this meaning is probably secondary. From Isa. 10.15 and Ezek. 19.13-14 it appears that a matteh was formerly a copper scepter hung up on a wooden staff.³2;
The term nahash is generally translated as 'serpent'. However, the closeness existing in Hebrew between nahash ('serpent') and nehoshet ('copper') suggests that nahash may also designate copper.³3; Accordingly, the prodigy performed 'in the name of Yahweh' becomes the transformation of a copper artifact (matteh, the scepter) into melted copper (nahash, the serpent). It is interesting to notice that such a 'prodigy' (occuring not so far from the camp of Jethro the Kenite) happens after Moses threw his matteh on a hot source, the 'burning bush', which may be a poetic evocation of live charcoal. If the reversible matteh-nahash conversion is considered in the book of Exodus as a specific sign of Yahweh, this implies that this deity was intimately associated with copper melting, at least in the period prior to the Israelite Alliance. (pp. 395-396)
from 'Yahweh, the Canaanite God of Metallurgy?', JSOT 33.4 (2009): 387-404
: The term matteh is explicitly used to designate the wooden staff in Exod. 17.16-23. But the initial meaning is revealed in Isa. 10.15, when it is asked, 'Shall the axe vaunt itself over the one who wields it, or the saw magnify itself against the one who handles it? As if a rod should raise the one who lifts it up, or as of a staff should lift the one who is not wood!' It a matteh cannot be hung up without a wooden staff, it is clear that it is not the wooden staff itself but something that is fitted with it. Furthermore, in his lamentation about the destruction of Israel, Ezekiel mentions the fact that the staff supporting the matteh will burn and will provoke a qeyna (Ezek. 19.13-14), a term designating the smelting of copper (and by extension its melting). This strongly suggests that the matteh is a copper-scepter. In some cases, traces of wood have been found in the inner space of the scepter, confirming that such items were probably borne upon wooden staffs.
: The term nahash is also used to designate copper in languages closely related to Hebrew (Ugaritic, Aramaic, Arabic). In the book of Chronicles, the term nahash is used once to designate copper: Ir Nahash was a town founded by a descendant of Celoub (Caleb), a clan of metalworkers (1 Chron 4.11-12), so that it designates the town where copper was smelted or worked.