What is their nature?

They require no physical nourishment [1] being sustained by the luster of the Holy Spirit, the Shechinah.[2] They are not troubled by the Yetzer Hara, the evil impulse, which means that they are not subject to normal human passions.[3]

Human beings are akin to the angels in three respects: "They have knowledge like the ministering angels; they have an erect stature like the ministering angels; they converse in the Holy Tongue (i.e. Hebrew) like the ministering angels."[4] On the point of language, with the exception of Gabriel, who was acquainted with every mode of speech, the angels were said to be ignorant of Aramaic; and for that reason one should not offer petitions for his needs in that language, since it was an angelic duty to carry the prayers which were uttered to the Throne of God.[5] (It has been suggested that there was a practical purpose behind that assertion, viz. the desire to preserve Hebrew as at least the language of prayer, although it had been displaced by Aramaic as the vernacular of the Jews.)

footnotes [1] Genesis Rabbah 48:14
[2] Exod. Rabbah 32:4
[3] Genesis Rabbah 48:2
[4] BT Hagiga 16a
[5] BT Sotah 33a