What are real examples of monopoly firms??
There are few, if any, firms that have monopoly power and which are big enough to be known to people around the world. This is because the vast majority of monopolies are local monopolies that are granted by governments.
Most monopolies are found in local areas and are granted by local governments. In the United States, for example, there are local monopolies in such things as the delivery of electricity, water, and local landline telephone service. There are typically monopolies in the delivery of cable television. Since each of these monopolies is localized, they are not held by large, famous firms.
The only firm that is known world-wide and could be considered a monopoly is Microsoft. Microsoft controls such a large proportion of the market for computer operating systems that it can be seen as a monopoly. It is not literally a monopoly as Apple has an operating system and there are open source operating systems. However, Microsoft does have such great market share that it has been prosecuted for antitrust violations in the European Union.