In Chinese Medicine the character for Metal (Jin) 金represents something precious deep in the earth. It includes the character for Earth (see below). The Metal character has a sloping roof on top, representing something covered over. You could imagine it as a mine with nuggets of gold buried deep within the earth. Metal can be thought of like minerals in the body. Small but essential. In the body the Metal Element consists of the Lungs and Large Intestine. The Lungs take in air. In Chinese Medicine they take in the Qi from the Heavens. The Large Intestine lets go of waste material. On a more emotional level it's important to be able to freely accept gifts and compliments. To appreciate beauty in the world. It's also important to let go of things we no longer need. The Dhammapada (sayings of the Buddha) states "For see how the Jasmine flower releases and lets fall its withered flowers." So we must release the parts of us that no longer serve us rather than clinging to them.
Recently I had the chance to go potholing with Lancashire Walking Group. We hiked up towards Ingleborough. Gaping Gill is part way up the hill. It is a huge cave with the longest unbroken waterfall in the country. You had to be winched down into it. It was really impressive. I have also recently visited Poole Caver in Buxton. It made me appreciate the nature of the Metal element.
Hicks, Hicks and Mole, 2004, Five Element Constitutional Acupuncture, Churchill Livingstone