Isabel Leonard . . . is so talented and accomplished that it is hard to believe she is only 34. She sings leading roles at the Met and elsewhere, from standard repertory to new works such as Cold Mountain. Her glamorous looks have made her a favorite on HD transmissions, but it is her singing and acting that leave the most lasting impression. She is stealing the show now as Cherubino in Le Nozze di Figaro at the Met, where she will sing Charlotte in Werther next season as well as Zerlina in Don Giovanni.