We're pleased to let you know that the 100.8 release of the ArcGIS Runtime SDK for iOS, coming soon out now, introduces Metal support. There's nothing you need to do to take advantage of this other than upgrade your version of the Runtime SDK for iOS to version 100.8.
Testing has shown improved performance (especially when displaying scenes in the simulator).
Because OpenGL ES support is no longer included, any development or testing workflow that uses the iOS Simulator must use a simulator that supports Metal to view an AGSMapView or AGSSceneView. What this means in practice is that to use version 100.8 with an iOS Simulator you must meet the following minimum conditions:
Developing on macOS Catalina (10.15)
Using Xcode 11 (this is a requirement for Runtime 100.8 anyway).
Simulating iOS 13
If you need to develop or test with version 100.8 against iOS 12 or using an earlier version of macOS, you need to use a physical device in place of the simulator.