I completely folded my knee in, tore everything, playing football a few years before I picked up skiing. My first season I wore a pair of fabric knee supports that had a metal/hard plastic support on the medial and lateral sides but honestly I think it was more of a mental brace than physical. The last couple seasons I've been focusing on pistol squats, stepups/downs, single leg straight deadlines, and hip mobility/strength stuff and I feel like that has provided far more protection than those fabric supports did.
Now you question asked about metal braces, after my knee injury I used a full metal donjoy brace while I played football and it was super supportive and gave a lot of confidence, but I moved from strong safety to d end. I was way slower and had far less agility. I've seen donjoys ski version of the metal brace and the main difference is a hyperextension prevention piece added to the joint. I would imagine that the ski metal brace is just as big of a blocker to agility and mobility as the football one was. Would not want to use it skiing personally
*single leg, straight leg deadlifts* couldn't edit that line for some reason
**This post was edited on Aug 20th 2022 at 11:42:05pm