This year, the pop-music world felt more wide open than ever. Our list of 2021’s best songs includes a beautiful indie-pop celebration of queer love, a reggaeton star tucking into some sweet Eighties synths, a self-celebrating pop-rap smash that scandalized the American right, a Lorde track that sounds like it could’ve been a Nineties U.K. club hit, and unforgettable anthems that pushed the bounda