This is mainly about a Microsoft stretched cluster & depends on the OS version. E.g. for 2008:
Your best bet will probably be on Node and File Share Majority, with the witness file share placed in a 3rd location.
For the MetroCluster itself you would normally trigger full site fail-over manually - there were some scripted automated solutions (using 3rd site with a witness), but I think support for it was always an a case by case basis.
Hmm, I've seen it briefly a while ago, but then forgot about it.
I'm still not sure about fully automated site fail-over, but the documentation says it is possible:
It's a bit of a mystery for me how it can be protected against a split-brain scenario without a 3rd site.