MGL is a graphics library that implements an OpenGL compatibility layer on top of Apple's Metal API. It translates OpenGL API calls into Metal rendering commands, allowing developers to use OpenGL-style programming on macOS without relying on legacy drivers. The library includes a shader compilation pipeline (GLSL to MSL via SPIR-V), a math library (GLM), and windowing support (GLFW). It is designed for high-performance rendering and virtualization contexts, evidenced by comments regarding QEMU framebuffer blitting. The codebase is a monolithic C/ObjC library with a dispatch table pattern for API routing.