Up and Running with Metal, Part 3: Lighting and Rendering in 3D (metalbyexample.com)

This is such a cool series. Except it hurts that I can try out the tutorials live because the "metal code" doesn't run on either the simulator or my A6 chip containing iPhone 5. Off by one generation :(

I'm not completely sure why I should learn metal instead of OpenGL. It doesn't seem that different.