How should Galatians 3:29 be understood in relation to Israel as God’s chosen people?

In Galatians 3:29, Paul writes: “If you belong to Christ, then you are Abraham’s seed, and heirs according to the promise.” How should this verse be understood in relation to other biblical passages that describe the Jewish people as God’s chosen people? Specifically, does Paul mean that believers in Christ (including Gentiles) are now included in the promises given to Abraham, or is he speaking in a different (e.g., spiritual or metaphorical) sense?