The Magic of Copper.
Copper used in Yantras and Bracelets.
Ancient seers in India have recognized that copper conducts heat and energy.
So, they made yantras on thin copper plates with mysterious geometrical patterns. Before copper, palm leaves were used but later it was discovered that Copper is efficient conductor and lasts much longer.
Since more than 2000 years, copper usage has become an integral part of Indian lifestyle.
Also according to Mantra Sastra, Mars (Mangal/Kuja) controls this science of mantras, yantras etc and the metal related to this planet is Copper.