Metal gauge refers to the thickness of metal. This can be applied to flat metal, round wire, half-round wire and any other raw metal with a standard thickness. When thinking of gauge, as the number gets bigger the thickness gets smaller.
For example, a very bulky bracelet could be a gauge 6. An average ring would be an 18. A thick man’s ring might be a 16. And a pendant or set of earrings could be 20 to 24 gauge.