A pair of artists that fans didn’t expect to form a close, musical relationship is rapper 2 Chainz and pop princess Ariana Grande. First, the Georgia rapper hopped on Grande’s remix to her hit song “7 Rings” before they linked up on 2 Chainz’s Rap or go to the League track “Rule the World.” Grande recently began her “Sweetener Tour” and has been taking arenas by storm, but the pint-sized singer surprised Boston fans when 2 Chainz came out on stage to perform “Rule the World” live for the first time ever.