Hey there @ironmosquito! Welcome to the community! This error is just letting you know that the Metal Toolchain (an additional download) is required. You can access this by accessing your Xcode Settings->Components->Metal Toolchain
Disclaimer: One or more of these links are unaffiliated with Epic Games. Epic Games is not liable for anything that may occur outside of this Unreal Engine domain. Please exercise your best judgment when following links outside of the forums.