Checked today.
Planets with 100% metal composition are just called "metal rich planet".
There are no others.
Thanks for double checking, I really didnt want to spend the rest of my life hunting a non-existing planet type. MYTH BUSTED
There are two types of metal planets. High metal planets, which are common as dirt, and metallic planets. Not sure if high-metal can be 100% metal but if you have seen then maybe so, but there are definitely ones that are called metallic and are always 100% metal and are worth a lot more.
Useless for mining though since we don't have planetary landings yet, but one with rings might be worthwhile.
I think they are "Metal Rich" not "Metalic"