Bright light, the speaker argues, keeps lovers stuck as they are. Under it, two people can't imagine themselves as winged, clawed, storm-tossed or slippery. Their cries sound like failed words, their sighs like a tired engine, and nakedness shrinks to "a mere absence of clothes," a magic trick with no magic in it.
So the poem turns into an invitation: hit the lights. Darkness becomes a way back to the body's "original habitat," a place older and wilder than the lit room, which the speaker calls a "walled garden." Desire here is partly about transformation, about becoming animal, element, something more than a separate self.
The mood is playful, intimate, and a little daring. The closing image of a rusty gate and the dark forest beyond feels both inviting and slightly dangerous, as though the speaker is leading the way out and hoping the other person will follow.