Final answer:
Guru Arjan Dev Ji first placed the gilt copper sheets on the Golden Temple, which is a major spiritual site for Sikhism. He was the fifth Sikh Guru.
Step-by-step explanation:
The Golden Temple, or Harmandir Sahib, is adorned with beautiful gilt copper sheets, and it was Guru Arjan Dev Ji who first placed these sheets on the temple. Guru Arjan Dev Ji was the fifth Sikh Guru and took a prominent role in the development of the Sikh religion. The Golden Temple serves as a central religious place of Sikhism and symbolizes equality and brotherhood. The temple's gilt copper sheets have become a part of its iconic appearance, attracting pilgrims and visitors from all over the world. Also, Guru Tegh Bahadur, mentioned in reference to your query, belonged to the Sikh religion.