According to the Bible, one does not simply join the church. God adds people to His church when they believe, repent, confess, and are baptized into Christ. The church is the body of Christ. Christ is the head, and the individual believers make up the members of His body.
||...And the Lord added to the church daily those who were being saved.
||And He put all things under His [Jesus'] feet, 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.
||There is one body and one Spirit, just as you were called in one hope of your
calling; one Lord, one faith, one baptism; one God and
Father of all, who is above all, and through all, and in you all.
||...Christ is head of the church; and
He is the Savior of the body.
|1 Corinthians 12:12-28
||For as the body is one and has many members, but all the members of that one
body, being many, are one body, so also is Christ. For by one
Spirit we were all baptized into one body -- whether Jews or Greeks, whether
slaves or free -- and have all been made to drink into one Spirit.
For in fact the body is not one member but many. If the foot
should say, "Because I am not a hand, I am not of the body," is it therefore not
of the body? And if the ear should say, "Because I am not an eye, I
am not of the body," is it therefore not of the body? If the whole
body were an eye, where would be the hearing? If the whole were hearing,
where would be the smelling? But now God has set the members, each
one of them, in the body just as He pleased. And if they were all
one member, where would the body be? But now indeed there are
many members, yet one body. And the eye cannot say to the hand, "I
have no need of you"; nor again the head to the feet, "I have no need of you."
No, much rather, those members of the body which seem to be weaker are
necessary. And those members of the body which we think to be less
honorable, on these we bestow greater honor; and our unpresentable parts have
greater modesty, but our presentable parts have no need. But God
composed the body, having given greater honor to that part which lacks it,
that there should be no schism in the body, but that the members
should have the same care for one another. And if one member
suffers, all the members suffer with it; or if one member is honored, all the
members rejoice with it. Now you are the body of Christ, and
members individually. And God has appointed these in the church:
first apostles, second prophets, third teachers, after that miracles, then gifts
of healings, helps, administrations, varieties of tongues.