Who will make up the nations in the millennial kingdom?
The nations in the millennial kingdom will consist of the large group of Jews who become the nation of Israel, along with a small remnant of Gentile believers drawn from every nation. Only believers enter the kingdom, serving as the seed stock for the Gentile nations under Christ the King.
Les explains that at the end of the tribulation, survivors who were unbelievers could not enter the kingdom, so Matthew 25 depicts this separation. The believers go in. A large group of Jews goes up to become the nation of Israel in the kingdom, and there is also a short smattering of Gentiles—just a few probably from every nation—the seed stock of the Gentile nations in the kingdom. Thus all nations are represented, but only believers enter. Christ is King of kings and Lord of lords; the twelve disciples rule over the nation of Israel, and members of the body of Christ rule with Christ over all.