Radiating elements are usually made of metallic materials which increase the antenna complexity and weight. In order to solve this drawback, an antenna manufacture process using metallized foams is presented. A microstrip patch antenna inspired in the fractal Koch island geometry embedded in a rectangular cavity is built and tested. Results of reflection coefficient and directivity versus frequency have been compared with simulated data resulting in very good agreement. All the metallic parts of the antenna (patch, cavity, and feeding probe) have been metallized on the foam resulting in a low weight, low complexity, and low cost antenna structure