Those who rise at the first resurrection will all be members of Christ’s church. This is not the same thing as saying that every member of every Christian denomination will be there. Let us be clear that we are talking about the mystical body of Christ, the company of all those who have received Christ as their personal Lord and Saviour. Those who rise will be members of the invisible body of Christ, as described by Paul in various places: “And He [God the Father] put all things under His feet [God the Son], and gave Him to be head over all things to the church, which is His body, the fullness of Him who fills all in all” (Ephesians 1:22-23). “For by one Spirit we were all baptised into one body, whether Jews or Greeks, whether slaves or free, and have all been made to drink into one Spirit” (1 Corinthians 12:13). “And He [Jesus] is the head of the body, the church, who is the beginning, the firstborn from the dead, that in all things He may have the pre-eminence” … “I now rejoice in my sufferings for you and fill up in my flesh what is lacking in the afflictions of Christ, for the sake of His body, which is the church” (Colossians 1:18,24). If you believe in Jesus Christ as your personal Lord and Saviour, and you are doing your best to walk and talk with Him daily, you are part of His Ekklesia (Church) irrespective of whatever earthly church or denominational affiliations you may or my not hold. It's good to be part of a local church, but mere local or denominational church membership saves no one!