Charm bracelets and charms have a long history, so long in fact, that the origins of such amulets are largely unknown. There is documented evidence that dates back to the age of the pharaoh, much of the explanations around which are conjecture but ancient Egyptians were certainly buried with trinkets and charms and many believe that such keepsakes were there to ward off negative energy to help the pharaoh on their journey to the land of the dead, and as an offering to gods upon arriving in the afterlife. Evidence suggests that the ancient Egyptian civilisation began around 5000 years ago but many speculate that amulets in the form of jewellery date back even further.
Indeed, many people believe that Neolithic men made use of stones, shells and wood to fashion jewellery that would then serve to ward off harmful spirits or to draw close positive spirits. There is some evidence to suggest that this may have been the case; elaborate bracelets have been discovered in various sites throughout the world - the exact purpose that such jewellery served is, of course, merely speculative but it is not beyond the realms of possibility that such items were used as charm bracelets in the modern understanding of their purpose, namely, to act as a form of protection against unknown negative forces.
More recently, but still a long time ago, the Romans made use of amulets in the form of jewellery. The most clearly documented style of amulet was the simple outline of a fish which we can still see today at many churches and which is used as a representation of Christianity. The fish is meant to symbolise the feeding of the five thousand by Jesus, on the shores of the Jordan River. It is argued that various groups within the Roman Empire - which was, at that time, predominantly Jewish - wore the symbol covertly and would reveal the charm when in the presence of other Christians in order to reveal their allegiance to the same religious order. These Christians needed to be able to hide their religion, while at the same time, be able to reveal it to others within the 'secret' order. In those days, within the Roman Empire, to be anything other than Jewish was judged heretic and blasphemous.
Much more recently, only 500 or so years ago, charm bracelets were used by the Kings, Queens, and Knights, of England. The Middle Ages is renowned for its belief in witchcraft and wizardry and so unsurprisingly, much of the population were concerned with the magic and mayhem that were being delivered to them by their foes. In battle, knights wore amulets to keep from harm and locked away in the security of their medieval castles the Kings and Queens wore amulets to keep enemies at bay and their fortresses safe from attack.
Nowadays, people wear charm bracelets largely as a form of decorative jewellery, however, many people do believe that charms afford them some kind of protection from negative energy and some kind of magnet for positive energy and this is particularly true of charms that make use of natural stones and gems. For sure, some charms do have an effect upon the wearer for instance, Amber is known to prevent the build up of static and protect from small shocks.