There is occasionally some discussion about the Seraphim. The word comes from a Hebrew verb, sarap, meaning to burn. They are thus the burning ones. That piece of information alone makes people think of fiery, flaming beings. That impression, however, is misleading. We will return to it a bit later.
The Seraphim are mentioned in Numbers 21:6-9; Deuteronomy 8:15; Isaiah 6:2-6; 14:29; 30:6. The reference in Numbers is the most familiar. The children of Israel complained about the lack of food (Number 21:5) and so God sent fiery serpents (hannechashim hasseraphim) [sorry, no time for diacritics] to bite the children of Israel (Numbers 21:6). When the people repented, Moses made a serpent of brass and placed it upon a pole and whoever looked at it lived (Numbers 21:7-9).
The Seraphim are thus a type of snake and, according to Isaiah 6:2-6, they have wings.
Here is a line drawing of an Israelite seal that shows a Seraph:
One can see the influence of Egyptian iconography on this Israelite Seraph.
Thus Seraphs are burning ones because their bites burn.