C5 does not support nested virtualization but i3.metal allows using virtualization technology without nested virtualization.
Both i3.metal and c5 use the same underlying Nitro technology.
Both i3.metal and c5 use the same underlying Nitro technology.
https://www.youtube.com/watch?v=o9_4uGvbvnk might be of interest - Matt Wilson talks a lot about the underlying magic of the bare metal instances.