One translation of Raphael's name is 'God Heals' and is described as the patron of travelers, young people, and the blind. In the series, Raphael has high self-healing ability, looks after the young Foll, and guided Kuroka when she lost sight(pun intended) of her path in life.
His sacred sword, Metatron, spewing flames could be a reference to:
"This Enoch, whose flesh was turned to flame, his veins to fire, his eye-lashes to flashes of lightning, his eye-balls to flaming torches, and whom God placed on a throne next to the throne of glory, received after this heavenly transformation the name Metatron."
Raphael supposedly resides over the sun so that could also be it...
