This Portrait of a man by the Master of the 1540s has known a remarkable history, both in terms of ownership and especially in its change of outlook, hence the title Metamorphosis. Since 1907 it has been part of a stylistically coherent group of portraits, given by Max J. Friedländer to the so-called Master of the 1540s in 1936. In this article I have tried to give a full account of the picture’s provenance history, the various restorations it underwent and the changes in its outlook which were the result of these restorations, making use of historical photographs as well as modern methods of examination, including infrared reflectography (IRR), X-radiography and Macro X-ray Fluorescence (MA-XRF). In addition the portrait is used as a tool to understand more of the artist’s working methods, including the possible use of detailed portrait drawings, a tool that must have been used by most active portrait painters at the time, although only drawings (and connected portrait paintings) by Hans Holbein the Younger and Jean Clouet have survived in such numbers that something useful can be said on the functions of both drawing and underdrawing. Finally, I have proposed an identification of the artist in question as Cornelis van Cleve, who was born in 1520 as the only son of Joos van Cleve. Together with Willem Key, Cornelis was probably trained in his father’s studio as a portrait painter. After his father passed away in 1540-41, the young Cornelis took over his father’s thriving studio. ; Le Portrait d'un homme du Maître des années 1540 a connu une histoire remarquable, tant du point de vue de la propriété que de son évolution stylistique, d'où le titre Métamorphose. Depuis 1907, il fait partie d'un groupe de portraits stylistiquement cohérent, attribué en 1936 par Max J. Friedländer au Maître des années 1540. Dans cet article, j'ai tenté de retracer en détail l'histoire de la provenance de l’œuvre, les diverses restaurations qu'elle a subies et les modifications de composition qui en ont résulté, en utilisant des ...