The main message of Philemon is a powerful appeal for forgiveness, reconciliation, and transformative love in Christ, urging slave owner Philemon to welcome back his runaway slave, Onesimus, not as property, but as a beloved brother in faith, effectively breaking down social barriers through the gospel. Paul uses this personal letter to illustrate how Christian fellowship (koinonia) redefines relationships, treating everyone as equals in God's eyes, demonstrating grace, and challenging worldly status. Key Themes & Messages:

• Radical Forgiveness: Paul asks Philemon to forgive Onesimus as God has forgiven them, a central Christian teaching. 
• Unity in Christ: The letter shows how faith in Jesus makes slaves and masters brothers, transforming former hierarchies into spiritual partnerships (Philemon 1:16). 
• Transformation of Relationships: It's a model for how the gospel changes everyday interactions, moving beyond societal norms to genuine Christian love and acceptance. 
• Grace & Reconciliation: The core concept is God's grace reconciling people, a principle Paul applies directly by asking Philemon to receive Onesimus "as you would me". 
• Practical Application of Faith: Philemon isn't just theological; it's a real-life example of living out Christian principles in difficult personal and social situations, as GotQuestions.org notes. 

In essence, Philemon teaches that Christian love demands reconciliation and equality, asking believers to extend the same transformative grace they've received to others, regardless of social standing.