Christmas 1933 (detail)

A detail of the "Christmas 1933" tapestry. If you look carefully here (and also the curtains), metallic threads were used.
It was already a possibility in 1930's. Just it's not true gold like in medieval times.
You must know a tapestry isn't only wool. It can be also threads of gold or silver, or silk. Even the size of the thread isn't the same. You can have large threads for generalistic parts (for example a frame around a tapestry); or very fine threads for details, such has faces (the most apparent case is in a tapestry of the Miyazaki's movies) to enlight those parts.
Also, when you see face to face a tapestry, some seems very delicate when you look them, probably because of colors. At the point you wish to touch them to see how soft they are. It's of course forbidden to touch them (despite some visitors who don't care and aren't happy we elevate the voice on them to insist on the STOP) like for any museum, but there are samples available in museum, and also in the Tolkien exhibition. A tapestry - all of them in fact - is rigid under fingers, believe me! (I was allowed to clean few dusts, and despite my efforts, my fingers reached the tapestries).