The first developer beta for macOS High Sierra dropped on June 5th, after the WWDC keynote address in which four operating systems were demonstrated, plus new Macs and new iPads. As Apple events go, it was filled with stuff, lots of stuff, and should thus be regarded as a rousing success.
But while iOS 11 has a load of front-facing improvements and enhancements — including the beginnings of decent iPad multitasking — macOS 10.13 may be regarded as somewhat of a subpar release on the surface. Beneath the surface, with Metal 2 graphics, a new file system (for some Macs anyway) and other enhancements will make for snappier performance.
Metal 2 graphics can yield a decided improvement if your Mac supports the technology. It allows the CPU and GPU to cooperate in providing better support for games and high power apps. Whatever Metal did, Metal 2 does better and adds additional functions.