Bare metal computers are simply traditional, physical computers. The "bare metal" part became needed as virtual computers (or virtual machines) became popular to distinguish physical computers from virtual ones.
VCL has the capability to provision bare metal computers by using xCAT. The bare metal computers need to have some sort of out of band management such as IPMI that is supported by xCAT in order for VCL to provision them. For security, the out of band management should be connected to a separate control network that the management node can access.