Important metaphors about the inclusion of the Gentiles:
The church is like a city, and Gentiles are full citizens (vv. 12a, 19a).
The church is like a household, and Gentiles are fully God’s children and full heirs (vv. 12b, 19b).
The church is like a building, and Gentiles are an integral part of the structure. The wording of versed 21-22 turns from “building” to “temple”, signifying the special way that God is constructing this structure (vv. 20-22).