How is Charlemagne's empire an example of cooperation between the Church and European monarchs?

Charlemagne's empire exemplifies cooperation between the Church and European monarchs through his close alliance with the papacy, particularly during his coronation as Holy Roman Emperor by Pope Leo III in 800 AD. This act not only legitimized Charlemagne's rule but also reinforced the Church's authority, positioning it as a central power in governance. In return, Charlemagne supported the spread of Christianity, established monasteries, and implemented Church reforms, thereby intertwining religious and political leadership to unify and stabilize his empire. This partnership helped shape the future of medieval Europe, merging spiritual and temporal authority.