What is the ruling on bestowing the title "His Majesty King So-and-So" or "His Most Exalted Majesty the King" upon the country's monarch, and what is the appropriate title for him if that is impermissible?

The beautiful names [of Allah] may share a common wording between Allah and His creation, so they are applied to Allah in a manner befitting Him, and to the created being in a manner appropriate to them, such as "the Forbearing" (al-Haleem) and "the Compassionate, the Merciful" (al-Ra'oof al-Raheem). Sheikh al-Islam Ibn Taymiyyah clarified this issue. Sheikh Ibn 'Uthaymeen mentioned that there is no harm in using titles such as "His Majesty" if the described individual is worthy of it and it does not lead to arrogance. As for Dr. Muhammad al-Khudairi, he believes that it is more appropriate to be moderate in praise, and that expressions of glorification such as "His Majesty" and "His Magnificence," if used, are for Allah alone. However, restricting them to a created being is permissible in a manner appropriate to them.