By Amy Lv, Winni Zhou, Ella Cao and Lewis Jackson SHANGHAI/BEIJING June 6 (Reuters) – Cargill is in talks to sell its metals unit to Macquarie Group, five sources with knowledge of the matter said, as the global trading house aims to focus on its core food and agriculture operations. All five sources spoke on condition of anonymity given the sale has not yet been announced and they are not authorised to speak to media.