Last year in June Apple announced that it would add support for external GPU’s to MacOS, and since a year the feature has finally arrived
With the latest update to MacOS High Sierra you can connect a number of different graphic cards via Thunderbolt 3 port and use the additional power to speed up various processes including games and video editing, Apple has highlighted that it’s use for VR
eGPUs are supported on MacBook Pro notebooks released in 2016 and later, iMac computers introduced in 2017 and later, and iMac Pro. Your Mac must also have macOS High Sierra 10.13.4 installed.
With eGPU support in macOS 10.13.4, you can:
More details can be found here