A reference to metal that Meryl brought up in the Brokeback tarot thread was the iron skillet that Ennis cooked Jack's breakfast in. I find it incredibly poignant to think of him cracking the eggs into that skillet, and applying the liberal amount of salt, checking to see if the salt was flowing freely. The iron in the skillet comes from the earth, so was appropriately the domain of Ennis. Iron was also the element that brought Jack down, in reality or in Ennis's imagination. Salt, another product of the earth, was also at Ennis's command, since he knew the "salty words" to The Strawberry Roan."
