Johnson made her professional debut at the Metropolitan Opera on November 20, 1985 as Lily in Gershwin's Porgy and Bess under the baton of William Vendice. She returned to the Met for more than 50 more performances over the next decade in roles like Serena in Porgy and Bess, the High Priestess in Aida, and Madelon in Andrea Chenier. Her last performance at the Met was in 1994 as the High Priestess.
