Seven months after declaring that advertisers pulling their ads from his social-media platform X could “go f— yourself,” Elon Musk took a more congenial tone onstage at the advertising industry’s most important annual festival.

Musk joined Mark Read, chief executive of ad giant WPP, in a session Wednesday at the Cannes Lions International Festival of Creativity in France, a five-day event that draws thousands of the industry’s chief marketing officers, tech leaders, creative workers and others from around the world. READ MORE