We are not told. In fact, we only know the names of two angels, despite many being mentioned in the Bible. The two named angels are Gabriel (Daniel 8:16;9:21; Luke 1:19,26) and Michael (Dan 10:13,21;12:1; Jude 9; Rev 12:7).
The angel in John’s vision sounds extraordinarily impressive:
Then I saw another mighty angel coming down from heaven, wrapped in a cloud, with a rainbow over his head, and his face was like the sun, and his legs like pillars of fire. 2 He had a little scroll open in his hand. And he set his right foot on the sea, and his left foot on the land, 3 and called out with a loud voice, like a lion roaring. When he called out, the seven thunders sounded. (Rev 10:1-3)
Some people have identified this angel with Michael (“the archangel”), but the only evidence for this is that they both sound important.
Other people have imagined that this angel is actually Jesus. But there is no evidence at all for that identification, or for any other angel being Jesus (see Heb 2:9).