A yarn consisting of one or more continuous lengths of metal strip or incorporating one or more continuous length(s) as a major component.
Note1: A notable example is a singles metal yarn in banknotes, which may be 0.50mm (0.020in.) wide and 0.08 mm (0.003 in.) thick. For this purpose, it must be without twist, i.e., flat throughout its length in the banknote. Analysis of the metal is proof of the authenticity of a banknote.
Note2: Twist inserted in flat metal yarns may form irregular facets, which reflect light accordingly to give decorative effects in fabrics
Textile Resource (http://www.textile.org.uk)