Knit fashions have really become ornate. Whether it's bejewelling or the surface "metallized", the added attraction has been embellishment.
Yarns blended or twisted with a lurex filament have been around forever, but a surface treated to look like "wet metal" is new, at least to me.
Ultimately, it reminds me of gilding furniture and frames with fine gold, silver or even iridescent foil sheets. The surface is painted with a substance that becomes tacky, helping the foil to adhere.
There are also very interesting new reflective yarns that can be blended with traditional yarns, especially effective with eyelash type yarns where the light peeks out under the eyelash fringe
Read further about iridescent pigments and how you can "paint" iridescence onto a surface.