Peter continues his instructions on submission in marriage,and sets some standards for beauty that are both amazing and controversial. This is true in our culture, and was likely true in his as well. You can see his standards in 1 Peter 3:3-4.
Peter is in the middle of his third area of submission, the area of marriage. Beginning with wives (he will address husbands shortly), he gives some standards about beauty, and how wives should strive for it. It’s helpful to note, that while this is applicable to all women, it is in the context of a passage specifically addressed to believing wives. Often, in our culture, when someone disagrees with this passage, they are coming from a different point of view than those to whom Peter is writing.
Peter equates beauty with modesty it seems,and does so much like Isaiah did a few centuries earlier, in Isaiah 3:16-24. Paul states something similar in 1 Timothy 2:9-10 as well. In our culture of exposure, many disagree with this. Their words are worth listening to and following, but at the same time, they should not be taken out of context either. Many mistakenly believe that Peter, along with Paul and Isaiah, are advocating the elimination of all outer adornment. But that is not the case; rather it means overly extravagant or ostentatious adornment.