All we know if an angel is that it is incorporeal, immaterial, and only by comparing it with God-who is incomparable-can we see that it has some density and body after all, since in reality only God is truly immaterial and incorporeal.
John of DamascusAn angel is an intelligent essence, always in motion. It has free will, is incorporeal, serves God, and has been bestowed with immortality. Only the Creator understands its true nature.
John of DamascusGluttony should be destroyed by self-control; unchastity by desire for God and longing for the blessings held in store; avarice by compassion for the poor; anger by goodwill and love for all men; worldly dejection by spiritual joy; listlessness by patience, perseverance and offering thanks to God; self-esteem by doing good in secret and by praying constantly with a contrite heart; and pride by not judging or despising anyone in the manner of the boastful Pharisee (cf. Lk. 18:11-12), and by considering oneself the least of all men.
John of DamascusHow can this come about?" Mary asked. "The Holy Spirit will come upon you," the angel answered, "and the power of the Most High will cover you with its shadow." And now you are the one who puts the question: "How can bread become Christ and wine His Blood?" I answer: "The power of the Holy Spirit will be at work to give us a marvel which surpasses understanding.
John of Damascus