“I will make your skies like iron and your earth like copper” (Lev. 26:19)
“Thy heaven that is over thy head shall be copper, and the earth that is under thee shall be iron. (Dev: 28:23)
We can appreciate that these are very evocative curses. Metals are unfeeling and unyeilding materials. Unlike the “waters” of the heaven and earth described in the beginning of the Torah, there is no fluidity in copper and iron.
This is important because we know that our mission is to unite, in holiness, the opposites of man and woman, humanity and Hashem, and, of course, heaven and earth. It is our job to bring these divided opposites together – and it is very difficult to do this when they are comprised of metals that are hard and resistant to whatever force we can apply to them.
But why, of all the metals known in the ancient world, brass and iron?
The answer is found in the first mention of the two metals: Tubal Kayin is the first person (Ber. 4:22) to use them to make cutting implements, like knives and swords.
Knives and swords are implements of division, of separation – the opposite of holiness.
When Hashem lays out the curses in the Torah, he is telling us that we, the Jewish people, would be so unable to create kedusha that the objects of our attention, heaven and earth, would themselves be made from materials that we use only for divisions! This is a curse indeed: that we would see no way to even make our lives meaningful according to the Torah itself.