Soyeuses translates to "silky" and is used to describe the texture of the angels' invisible wings in the song.
It's a beautiful and evocative adjective that adds a touch of softness and mystery to the imagery of angels. While not extremely rare, its specific use here to describe invisible wings makes it particularly memorable and unique to the song's theme.
Have you ever met someone who felt like an angel? Carla Bruni sings about those rare moments when, on a lucky day, "il arrive que l'on croise un ange" (it happens that we meet an angel). These aren't heavenly beings with visible wings; she warns that "les anges ressemblent à tout le monde" (angels look like everyone else). They appear on our worst days, when life feels as fragile as "une feuille d'automne" (an autumn leaf), and offer comfort. They are a sudden relief from the "morsure de l'angoisse" (bite of anguish).
But here's the twist. The song isn't just about finding comfort, it's about our very human, very selfish reaction to it. Bruni admits we can't help but want to "l'emprisonner / Rien que pour soi le garder" (imprison them / To keep them only for ourselves). It's a possessive, almost desperate feeling. So, she ends with a warning: "gare à ne pas tomber amoureux" (beware of falling in love). Meeting an angel might save you for a moment, but trying to own them could be your downfall.