Proteuo (πρωτεύω) means to be first, to hold first place, or to have supremacy. It appears only once in the New Testament (Colossians 1:18), where Paul applies it to Christ in the most exalted possible way: 'so that in everything he might have the supremacy [proteuo].' This single occurrence carries one of the highest Christological claims in the New Testament.
Colossians 1:15–20 is the great Christological hymn, and proteuo is its apex. Paul establishes Christ's primacy in two spheres: creation (1:15–17) and redemption (1:18–20). In creation, He is the 'firstborn [prototokos] over all creation,' through whom and for whom all things were made. In redemption, He is the 'firstborn from the dead' — the first to be permanently resurrected — 'so that in everything he might have the supremacy [proteuo].' Jesus holds first place in every category. The universe was created for His glory; the church was purchased by His blood; history is moving toward His throne. Demetrius in 3 John 9 claimed to be 'first' among the church — but proteuo belongs to Christ alone.