In 1047, he succeeded his uncle Dietrich II (d. 30 April 1047) as Bishop of Metz.
He distinguished himself by his piety, his education, the prudent manner in which he administered his bishopric and his political influence.
Later the people of Rome elected Bruno by acclamation, and he became Pope as Leo IX.
Adalbero III was also present at the council in Rome in 1050 where Bishop Gerard of Toul was canonized.
Emperor Henry IV enfeoffed Adalbero with the County of Saarbrücken.