If you're speaking of state-sanctioned monopolies, you mean royal letters patent. This is from the Latin, litterae patentae: open letters, ( as opposed to private ones) because they were addressed to the public at large.

They had a pretty varied role. In England before the Tudor period, there were "letters of protection": simply the monarch encouraging foreign tradesmen to come and establish a craft or trade that England didn't have- and, of course, take on English apprentices to learn it. But there wasn't a monopoly associated with it until the Tudors brought over Italian glass makers. There was already something of a patent system among the Italian city states, that would grant an inventor ten years of exclusive use of something they'd developed, and when Italian glass makers were brought in, they demanded the same sort of exclusivity (this Italian practice seems to have generally caught on, around Europe). So, for a while in the 16th c. letters of patent were a way of importing new technology which England lacked, like glass making , mining, metallurgy, and textiles- and that would mean England could import less glass, iron, cloth, etc. But there was also a tendency to avoid trampling on established industries- someone foreign with a new way to make salt was denied a patent, for example, because someone English already was making salt. So the use of the patents for bringing in technology gradually waned: as, say, English glass makers became established, someone foreign with only an improved way of firing a glass furnace had less a chance of getting a monopoly, because it would hurt the established businesses.

As the use of patents for importing technology grew less ( and requirements about educating apprentices etc. were dropped) , the nobility's use of the patent system ( or lack of it) for their own aggrandizement increased, notably under Elizabeth I. Like any monarch of the time, Elizabeth was always under some pressure to confer favors to gain support from her most powerful subjects, and reward others she felt deserved it. There was a finite amount of land to grant, and she only had so much money at hand: but new monopolies could always easily be created, and she did. Novelty of design was not critical... A courtier could get a monopoly for a coal mine. Instead of being paid to be court composers, Thomas Tallis and William Byrd were granted a 21 -year patent on printing music paper. By the end of her reign, there was a lot of grumbling about the system being abused, only being a patronage device: but that patronage still continued under James I, and the grumbling increased. It was cheap, as patronage goes, but it was costly, too: it favored one influential person at the expense of one less influential, and by the early 17th c., the King was faced with the typical problem of favoring one subject over another- it created one ungrateful man, made a hundred envious, a hundred more furious, and didn't bring in much money. As the Earl of Clarendon later succinctly put it, in his History of the Civil Wars

"Projects of all kinds, many ridiculous, many scandalous, all very grievous, were set on foot; the envy and reproach of which came to the King, the profit to other men".

Parliament enacted the Statute of Monopolies in 1624 to correct some of the abuses ( you could obtain a Patent to Register alehouses, for example, so anyone opening one had to apply to you). It didn't really fix things, though. Clarendon thought it to be one of the grievances against the King causing the English Revolution. The Long Parliament then limited the system some more, and it diminished during the Interregnum, but despite greater and greater public indignation, once he was on the throne after the Revolution Charles II would still grant monopolies. Monopolies were finally decisively doomed when a court denied the right of the East India Company to exclude other merchants from its established trading territory in 1684, the last year of Charles' reign. "Monopoly" by then had become a very odious word. Although the patent system would suffer from excessive royal and government interference ( say, preferring to grant more patents that suited a military purpose) , in the early 18th century it had really stopped being a patronage system, became more the legal protection of intellectual property that it is today.

Christine MacLeod; Inventing the Industrial Revolution: The English Patent System, 1660-1800