In verse 2 we read, "And above [the throne] stood the Seraphim." These were bright, burning beings, and it looked as though each one had six wings. I do not imagine these were actual wings, but maybe flames. How else do you describe a flame? The flames would look like wings. These were glorious, radiant beings. Two "wings" covered their faces, two covered their feet, and two were used to fly. One cried to another and said, "Holy, holy, holy, is the Lord of Hosts; the whole earth is full of his glory. And the posts [the pillars] of the door moved at the voice of him that cried, and the house was filled with smoke." The smoke was probably incense, or perhaps some kind of smoke connected with the fire at the altar.