One of the answers is colloidal gold. It was not just a shiny metal, it was used for many purposes, including drinking water with microscopic specks of it (as weirdly as it sounds). According to Wikipedia:

Used since ancient times as a method of staining glass, colloidal gold was used in the 4th-century Lycurgus Cup, which changes color depending on the location of light source.

During the Middle Ages, soluble gold, a solution containing gold salt, had a reputation for its curative property for various diseases. In 1618, Francis Anthony, a philosopher and member of the medical profession, published a book called Panacea Aurea, sive tractatus duo de ipsius Auro Potabili (Latin: gold potion, or two treatments of potable gold). The book introduces information on the formation of colloidal gold and its medical uses. About half a century later, English botanist Nicholas Culpepper published a book in 1656, Treatise of Aurum Potabile, solely discussing the medical uses of colloidal gold.

Edit: it’s worth mentioning that it’s not so weird to imagine if we consider that our diet requirements include many metals, such as copper (important to the hair), zinc and, especially, iron which composes our blood (even though it’s a different atom of iron than the iron from metallurgy, it’s “iron” anyways).