David Connolly quotes:

In their role as celestial servants to humans on earth, Angels act variously as guardians, guides, teachers, truth-givers and comforters, protectors of the righteous, punishers of the wicked, and more.

Through the 13th century, paintings of Angels exhibit a predominantly masculine appearance. Over the next 300 years, their images become more delicate, gentle, and feminine, until Angels are shown as androgynous or even distinctly female.

In freely choosing to serve as the agents of divine purpose, angels are the living expression of the prayer 'Thy will be done.'

The higher orders [of angels] are presumed to be closer in their nature to God and to function in roles that serve God more directly than the lower orders, which tend to the administration of the physical universe and the service of humankind. Some orders are associated with particular divine qualities - Seraphim with Love, Cherubim with Wisdom, Thrones with Judgment.