In creating jewellery, gemstones, coins, or other precious items are often used, and they are typically set into precious metals. Alloys of nearly every metal known have been encountered in jewellery. Bronze, for example, was common in Roman times. Modern fine jewellery usually includes gold, white gold, platinum, palladium, titanium, or silver. Most American and European gold jewellery is made of an alloy of gold, the purity of which is stated in karats, indicated by a number followed by the letter K.

American gold jewellery must be of at least 10K purity (41.7% pure gold), (though in the UK the number is 9K (37.5% pure gold) and is typically found up to 18K (75% pure gold). Higher purity levels are less common with alloys at 22 K (91.6% pure gold), and 24 K (99.9% pure gold) being considered too soft for jewellery use in America and Europe. These high purity alloys, however, are widely used across Asia, the Middle East and Africa.^{[citation needed]} Platinum alloys range from 900 (90% pure) to 950 (95.0% pure). The silver used in jewellery is usually sterling silver, or 92.5% fine silver. In costume jewellery, stainless steel findings are sometimes used.

Jewellery has been used for a number of reasons:

• Currency, wealth display and storage,
• Functional use (such as clasps, pins and buckles)
• Symbolism (to show membership or status or religious affiliation)
• Protection (in the form of amulets and magical wards).
• Artistic display

Most cultures have at some point had a practice of keeping large amounts of wealth stored in the form of jewellery. Numerous cultures move wedding dowries in the form of jewellery or create jewellery as a means to store or display coins. Alternatively, jewellery has been used as a currency or trade good; an example being the use of slave beads^.

Many items of jewellery, such as brooches and buckles, originated as purely functional items, but evolved into decorative items as their functional requirement diminished.