From Philippians, Colossians, Philemon by Dennis Hamm, SJ, commenting on Philippians 2:5-11:
The passage as example. The first and best application of this passage is the one Paul himself makes in the Letter to the Philippians. The Christ hymn illustrates the mind-set he exhorts Christians to take on in the preceding verses (1:27–2:4). Then in the verses that follow (2:12–18) he will apply the example of Christ in concrete ways to the life of the community.
The passage as a prayer of the Church. The passage has such beauty and wholeness that it lends itself to being lifted from its epistolary context and used as a freestanding text for prayer, meditation, liturgical reading, and song. Indeed, it is likely that more Christians have experienced the text in these contexts than in the context of the letter itself. In that way, it is like the three canticles drawn from the infancy narrative of the Gospel of Luke—the Magnificat (1:46–55), the Benedictus (1:68–79), and the Nunc Dimittis (2:29–32).
The passage as a source of doctrine. Paul speaks of Christ as being “in the form of God” and not considering “equality with God” as something to be taken advantage of. In all this, he refers to the preexistent, eternally divine Son of God in a way that parallels the thought of Heb 1:1–14, the prologue of John (1:1–4), the affirmation of 1 Cor 8:6, and the hymn of Col 1:15–20. It is important to notice that Paul is not teaching the preexistence of the Son as something new. He presumes that this is common knowledge among Christians as he moves to present first Christ’s self-emptying in his †incarnation and then the self-humiliation of his earthly life and shameful death as the pattern and standard for the life of a Christian.
While Paul is not explicitly spelling out the doctrine of Jesus as Second Person of the Trinity, his text provided some of the raw material that the Church, some three centuries later, would use to formulate the doctrine of Jesus as the eternal Son “consubstantial” with the Father.