This formulation is a reminder of the angel of Revelation 8:5 who took fire from the altar, threw it on the earth, and so triggered God’s judgments. As the one who has authority over the fire,
the angel of Revelation 14:18 has God-given authority to bring judgment on the earth. That is what he proceeds to do.
18 And another angel came out from the altar, the angel who has authority over the fire, and he called with a loud voice to the one who had the sharp sickle, “Put in your sickle and gather the clusters from the vine of the earth, for its grapes are ripe.”