Albert Barnes Commentary 1 Kings 11:28

"And the man Jeroboam was a mighty man of valor; and Solomon saw the young man that he was industrious, and he gave him charge over all the labor of the house of Joseph." — 1 Kings 11:28 (ASV)

A mighty man of valor: Here, the phrase means "a man of strength and activity." It is a general term of commendation, and its exact meaning must be determined by the context (1 Samuel 9:1).

Solomon appointed Jeroboam as superintendent over all the forced labor (referred to as "the charge") that was required from his own tribe of Ephraim. This appointment was made while Solomon was building the Millo and fortifying the city of Jerusalem (1 Kings 9:15).