When they entered Italy the Lombards were partly still pagan, partly Arian Christians, and hence got along very badly with the Roman Catholic Church. They were not converted to orthodox Christianity until after the year 600.
The last Lombard King of the Lombards was Desiderius, who ruled until 774, when Charlemagne not only conquered the Lombard kingdom, but in an utterly novel decision took the ethnic title "King of the Lombards" as well. Before then the Germanic kingdoms had frequently conquered each other, but none had adopted the title of King of another people.
Much of our knowledge of the mythological and semi-mythological early history of the Lombard people comes from Paul the Deacon's History of the Lombards, written in the late 8th century.