Answer:
False.
Step-by-step explanation:
The monarch (currently King Charles III) is not the Chief Executive.
The United Kingdom is a constitutional monarchy where the power to make and pass laws lies with an elected Parliament. The Prime Minister and Cabinet hold executive power and are responsible for running the government.
There are lots of other constitutional monarchies.
Countries like Liechtenstein, Monaco, Morocco, Jordan, Kuwait, Bahrain, Australia, Canada, the Netherlands, Spain, Belgium, Sweden, Malaysia, Thailand, Cambodia, and Japan.