Morning,
Quoted from Fundamentals of Catholic Dogma by Dr. Ludwig Ott.
** The nature of the angels is spiritual. [De Fide]**
The 4th Lateran and the Vatican Councils speak of a spiritual and a corporeal creation and refer the former to the angels.
As distinct from human nature, which is composed of spirit and body, the nature of the angels is purely spiritual, that is free from all materiality.
Holy Write explictily calls the angels spirits. See 3 Kings 22:21; Daniel 3:86; Wisdom 7:23; 2 Macc. 3:24; Mt. 8:16, Luke 6:18, 10:20, 11:24, Heb 1:14; Apoc 1:4 St. Paul contrasts “the spirits of wickedness,” that is, the fallen angels, with “flesh and blood” that is, mankind. Eph. 6:12: “We must not wage battle against flesh and blood but against the principalities, against the powers, against the rulers of the world of this darkness, against the spirits of evil in the world of heaven.” The act of contrasting shows that the fallen agnels are visualised as immaterial essences.
[ommiting a paragraph]
A great number of the Fathers, ascribed to the angels a fine ethereal or firelike corporeality.
Catechism of the Catholic Church
Paragraph 328 - The existence of the spiritual, non-corporeal beings that Sacred Scripture usually calls “angels” is a truth of faith. The witness of Scripture is as clear as the unanimity of Tradition
very succinctly put.
I would also recommend you to look up in the Summa Theologia about the parts where it talks about angels being pure spirits.
Hope this helps.
God bless.