Normal for Metal to Show on Cap/crown?

As you know, the most important reason to have a crown/cap placed is that it will strengthen and protect your tooth.  Some crowns have a metal structure under the porcelain and depending on the design, can show through.  In the lower molar area, it's pretty hard for anyone to notice the esthetic concern of metal show, however there are other materials available that do not contain metal and have excellent strength as well as esthetic appearance. It's likely that the material was chosen for a reason, so as with any dental problem, the best place to start is by having a conversation with your dentist.

A metal ring is common around some crowns-particularly in the back teeth. Although it may seem unaesthetic to you, it usually will not lie in the visible smile zone so will go unnoticed when you smile. Metal-porcelain crowns are  kinder to the teeth, in that a lesser amount of tooth structure needs to be removed to place them. If the crowns fit well and are functional, it might be a good option to leave them as such, as removing them might cause further trauma to your teeth. If you are still unhappy, then a discussion with your dentist would be the obvious thing to do. But bear in mind, your dentist has acted with your best interests at heart. Good luck!

A dental crown, also called a cap, is a sheath that fits snugly over the entire visible surface of the tooth, essentially giving your tooth a new surface. This allows it not only to give the tooth an attractive appearance, but to add support and strength. Most importantly, the crown seals the damaged tooth, protecting it from harmful bacteria. PFM crowns give a good compromise of strength and appearance. They look like porcelain crowns and are strong like metal crowns. All-porcelain crowns are slightly more attractive than PFM crowns as they have a more natural luster, better color matching options, and will not show metal if your gums recede or if the crown experiences wear.

Crowns are used to repair teeth when there has been extensive damage.

In my opinion, we are now in an age where we no longer need to crown teeth and leave dark lines or dark edges. Research has been very revealing about the strength of our current non-metal crowns. In most situations, there are crowns that are all white and leave no dark edge.

Like any other disappointment, contact your dentist. In a calm manner, ask the same questions and listen to why they chose this for you.

At this point, as long as the crowns fit extremely well, then you may want to leave them alone and nor risk irritating the teeth more by having additional dental work.

WIth nearly EVRY dental procedure, there are options on what you can have placed in your mouth. A great dentist who knows you well, can help guide you to the best choice for you.

The metal you are referring ti is called a metal collar is the thin metal usually a little more friendly to the gum tissue.  By increasing the tooth preparation you can use a new porcelain or product that would solve that issue.  Other than the esthetics there should be no issue leaving the crown intact.