Metal Core PCB is the metal core object for PCBs. 
It is infused from a technology developed to overcome the thermal limitations. 
Most of these PCBs are made of Aluminum core, copper core, and Steel Alloy.

The purpose is to forward the heat from the critical board components to the lesser critical areas.

Base materials of MPCB are the alternative to FR4 or CEM3 boards.
The metal core is far better than the FR4 boards and able to perform at high temperatures.
There is another type of metal-based PCB that is Insulated Metal Substrate PCB that is effective for electrical isolation between the copper and metal core. 
It uses a special dielectric specifically customized for high thermal conductivity.