Grésillent comes from the verb grésiller, which describes a light crackling or sizzling sound, like a gentle fire or static electricity. It's a very sensory and somewhat rare word that paints a vivid sonic picture.
In the song, the singer says "Je n'aime que tes bas résilles / Qui dans mes pensées grésillent" (I only love your fishnet stockings / Which crackle in my thoughts). This creates a strange and captivating image: the stockings generate a kind of electric, sizzling static in his mind, suggesting an obsessive and almost physically charged desire that haunts his thoughts.
VIDEOCLUB hands you pure teenage romantic obsession in "Roi", starting with a humble brush-off: "T'en trouvera d'autres des mecs comme moi / Il y en aura plein des gars pour toi" ("You'll find other guys like me / There will be plenty of boys for you"). Notice the casual everyday slang here: mecs and gars both just mean "guys" or "dudes" in French. But do not let that modest opening fool you. The rest of the song completely drops the chill act, dialing up a fantasy where the speaker tracks their lover through dreams ("Je te traque dans mes rêves"), calls them a precious "rubis saphir" ("ruby sapphire"), and begs to be loved across every season, weather condition, and skin tone: "Aime moi dans la neige / Aime moi sous le soleil / Aime moi la peau beige" ("Love me in the snow / Love me under the sun / Love me beige skin").
By the bridge, the devotion turns into total tunnel vision. One voice claims to be a creature of the dark ("Je suis un garçon de la nuit" ["I am a boy of the night"]) who ignores all other girls, obsessing solely over fishnet stockings that buzz inside his head: "Je n'aime que tes bas résilles / Qui dans mes pensées grésillent". Everything outside their private world tastes bland or sickeningly sweet ("Je déteste le goût mièvre de leur bouches" ["I hate the bland taste of their mouths"]). Surrounded by envious crowds, wandering through rain and smoke, the singer feels like absolute royalty purely because of love: "Avec toi je suis roi" ("With you I am king"). It is dramatic, dramatic to the point of being a bit over-the-top, and completely honest about the dizzying high of young devotion.