Is it forbidden for men to wear necklaces and bracelets, even if they are made of silver? And is it forbidden for them to wear cowrie shells?

It is absolutely impermissible for a man to wear necklaces and bracelets, as this constitutes imitation of women. The cowrie shell (wada'ah) takes the same ruling, and the matter becomes worse if wearing it is accompanied by a belief in bringing good luck or warding off the evil eye, for the Prophet, peace and blessings of Allah be upon him, said: "Whoever wears an amulet, may Allah not fulfill his need; and whoever wears a cowrie shell, may Allah not grant him peace."