Jamieson, Fausset and Brown on Revelation 2:18

18. Thyatira--in Lydia, south of Pergamos. Lydia, the purple-seller of this city, having been converted at Philippi, a Macedonian city (with which Thyatira, as being a Macedonian colony, had naturally much intercourse), was probably the instrument of first carrying the Gospel to her native town. John follows the geographical order here, for Thyatira lay a little to the left of the road from Pergamos to Sardis [Strabo, 13:4].

Son of God ... eyes like ... fire ... feet ... like fine brass--or "glowing brass" (see on Re 1:14,15, whence this description is resumed). Again His attributes accord with His address. The title "Son of God," is from Psa 2:7, 9, which is referred to in Re 2:27. The attribute, "eyes like a flame," &c., answers to Re 2:23, "I am He which searcheth the reins and hearts." The attribute, "feet like ... brass," answers to Re 2:27, "as the vessels of a potter shall they be broken to shivers," He treading them to pieces with His strong feet.