Keys symbolize access to special knowledge that gives someone authority (see Matthew 13:16–17; 23:13; Isaiah 22:22; Revelation 3:7).
bind … loose: Jesus gave Peter (and later the rest of the twelve apostles, Matthew 18:18) the authority to teach God's will as Jesus Christ revealed it (13:52; 18:15–20; 23:2–12; 28:16–20).
will be: You could also translate this as will have been. This emphasizes that God’s sovereign decision comes first.