Métamorphose means "metamorphosis" or "transformation". It's a beautiful and dramatic word that evokes a profound change, much like a caterpillar turning into a butterfly.
In this song, the singer describes the emotional turmoil of loving two people. She sings, "Mon coeur se métamorphose" (My heart transforms), using this powerful image to express how her feelings dramatically shift from one person to the other, as if her heart is constantly changing its very nature.
Ever felt like you were two different people at once? In "Vice Et Versa," Stéphane sings about being torn between two lovers, but with a twist: her feelings change depending on where she is! She sings, "Je t'aime ici mais là-bas / Je ne t'aime pas" (I love you here but over there / I don't love you). One minute she's walking through Montreux, smiling for a photo with one person, and the next she's in Paris wanting to give a rose to someone else. It's a dizzying back-and-forth, perfectly summed up by the title, which means "the other way around."
She even tries to label the situation, calling it "Polyamour, c'est le feu / Mais c'est toujours une de trop" (Polyamory, it's fire / But it's always one too many). She acknowledges the excitement but admits it's just not working. Underneath the upbeat tune, she's struggling to keep it together, admitting "Je fais semblant de gérer" (I pretend to manage) while her trembling hands give her away. It's a refreshingly honest look at how confusing love can be, and how exhausting it is to feel your heart constantly changing its mind.