This page explains how to find the Ka'o Makagh shrine and solve the "Metal Doors Open the Way" puzzle.
How to Reach the Shrine
Go to Pumaag Nitae Shrine and go to the nearby fork in the road, and go south there. The road will lead you to this shrine.
How to Solve the Shrine
Use Magnesis to open the doors. Be warned: there are Guardian Scouts in the next area. There are also more metal doors in the left wall of this area. One of the doors is attached to cracked blocks. Use remote bombs to blow them up. Go past those metal doors to find a chest that contains a Traveler's Bow. Then use Magnesis to lift and move the door that was attached to the cracked blocks. Use the door to knock down the pillar of stones that a treasure chest is sitting on, on one of the nearby platforms. The chest contains an Opal.
There is a hidden chamber in the platform that the chest was on. Go around that platform using Magnesis to find a secret magnetic block in the wall. Pull it out and climb into the hidden room to find a chest that contains a Gold Rupee.
Now use Magnesis to take the metal door to the platform that has stairs leading up to it. Go up the stairs and use the metal door to make a bridge between the current platform and the other one between here and Ka'o Makagh. Then go across the metal door and move it so it creates a ramp up to Ka'o Makagh.