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 an efficient conductor and lasts much longer.
Since more than 2000 years, copper usage has become an integral part of Indian lifestyle. Many gurus wear copper and encourage yogi's (meditators) to wear copper for the energetic benefits. Some say wearing copper during meditation helps connect to other dimensions.
Also according to Mantra Sastra, Mars (Mangal/Kuja) controls this science of mantras, yantras etc and the metal related to this planet is Copper.
If someone suffers from excess heat in the body due to mars in their horoscope, or excess pitta (ayurvedic dosha imbalance), it is advised to wear a copper bracelet on active hand’s wrist.
This helps them balance the body temperature as they start sweating during the day and green color layer, similar to copper-carbonate or verdigris (washable) forms on the skin where copper bracelet touches it.
They should also drink copper vessel stores water everyday.