Hello Ev!
Online I found some conflicting sources about the higher metallic value you can use inside a PBR. Some of these tell keeping it between 0 and 0.7 avoid performance and visual issues, especially with Lumen, in a scene where, for example, there’re many metallic objects closer one another.
While, Epic say : “you should set Metallic to either 0 or 1, not anything in between.” and “ You may be reluctant at first to make any Material completely metallic. Resist the impulse to use partial values unless you have a good reason. “ , nothing about possible problems in using metal at 1 and recommendations on how to avoid them.
So, I’m a bit confused 
. Maybe I missed/misunderstood something? Can someone help me to clarify these doubts? 
Ty’all! 