Metal island films are widely-used as reflection layers in optics and optical data storage. Their optical properties are dominated by the effect of plasmon resonance and, thus, by size and shape of the metal islands. By altering size and shape of these islands, the optical properties of the metal films can be adjusted. Depending on the wavelength range and type of metal, the film reflectance can be either increased or decreased. It is shown that changes in size and shape can be caused by means of a laser. This allows a well-defined adjustment of the optical properties of thin metal films. The optical properties can be adjusted locally. This technique can be used in different fields such as holography, adaptive optics or multi-layer optical data storage.