Peter begins his epistle by reminding the readers of salvation. The first five verses he refocuses his audience on the glorious salvation. (You can read more here).
The author beginning in verse 6 is still concerned with the salvation we have received, the glorious grace given to us. In his concern he wants to show how suffering can fit into a doctrine of salvation (soteriology).
Suffering’s Role in Salvation
Peter views suffering as an opportunity to show the genuineness of our faith. Just like putting gold and silver through fire shows the genuineness of the precious metal, our faith is found genuine when we endure trials and stay faithful (verse 7).