Reproduction steps:
1. Create a new Unity project.
2. Create a new scene.
3. Select "Metal" graphics API.
4. Build and run the created scene for OSX standalone (Check the screenshot).
- Screen is covered with transparent net.
- Random white and pink stripes appears on the screen.

Reproduced with:
5.4.1p3
5.5.0b5
OS X 10.11.6 3,3 GHz Intel Core i5 8 GB AMD Radeon R9 M395 2048 MB iMac (Retina 5K, 27-inch Late 2015) (My machine)

Not reproducible with:
5.3.6p6
OS X 10.11.6 Intel Core i5 3,5 GHz 8GB AMD Radeon R9 M290X 2048 MB iMac (Retina 5K, 27-inch, Late 2014)
OS X 10.11.6 2.4 GHz Intel Core i7 8 GB NVIDIA GeForce GT 650M 1024 MB MacBook Pro (Retina, 15-inch, Early 2013)