This is not a metaphor

Da Vinci thought it was an ordinary canvas. What he did not realize was that the sheet was threaded with angel wings and stardust strands, frozen with time and enveloping an electric connection. Each painted stroke had an equal and opposite effect on the back of the canvas, sent through by the pinpricks of light and energy (which is understood to happen when working with natural surfaces) but not seen because it had already been mounted on a mahogany support. He painted what he saw already in the canvas, his reflection, in the eyes of a water nymph. A skeleton of whispered promises gave her cheeks depth and sunk her eyes, the faint rose of her lips a telltale sign of stolen fruit and sweets, and a fleeting glow ebbing deep from her collarbone where the angel wings unfroze and shivered, not wholly free, and not wholly warm, either.