Let us consider Rust, the blood of iron.
It is Red, and thus partakes of the nature of life-force and power that is common among red things: blood (which in itself contains iron), the berries of Rowan, red ocher. So, one might use it in work devoted to Becoming, and the manifesting of Might.
It is Iron, and thus partakes of the nature of Power, might and force that iron, metal of Mars and warfare and warding, does. So, one might use it in work devoted to fortification, destruction, and strength.
It is Rust, and thus partakes in the nature of dissolution and decay, as the oxide of iron eats away at the substance of the metal itself. So, one might use it in work devoted to decline, entropy, or erosion.
A few weeks ago, I was standing in the shower and noticed that the plastic coating on my shower caddy was splitting. Water had wicked in at some point, and a slow small bloom of rust had begun at that spot. As I stood, I prodded it with my finger, and thought, forcefully and of a sudden, “Let us consider Rust…” You never know when inspiration will descend.
I have added rust to my ‘Things to Gather in Spring’ mental list. I don’t have a specific use for any right now, but gather I will.