Embroidery using metal threads is often generally referred to collectively as goldwork. Popular colors for this type of needlework are gold, silver and sometimes copper. The example shown here is actually worked in silver threads.
Goldwork is a type of surface embroidery in which metal threads of different types and sizes are laid or attached to the surface of the fabric using couching stitches. The ends of the metal threads are tucked to the back side of the fabric in most cases, so they are not visible on the surface.
The metal threads used in goldwork are not your craft store or sewing center variety of metallic embroidery threads. Metal threads used in this type of embroidery are very specific and include passing (a metallic thread wrapped around a strong, cotton core), rococco or crinkle cordonnet (which have a kinked look), buillion or pearl purl (a spring-like thread that can be pulled or stretched), frieze and faconnee (which has a faceted, jewel-like look to it), Jaceron or Pearl (which looks like a fine string of beads) and others.
To work the design, the artist cuts the metal threads into small pieces and appliqued them to the surface of the embroidery fabric using a very fine - nearly invisible - thread. Good quality metal threads can be expensive and goldwork is is considered an advanced technique requiring hours of practice.