On the P200 machine we routinely test with, the game ran well with only a few noticeable slowdowns in the heat of intense combat. Metal can be mined using automated mining equipment if you can find a good ore vein. You can also create metal, albeit slowly, from energy using a special building. Interestingly you can also recover metal from the wrecked hulks of units destroyed in combat. In fact, in many cases this may be your primary source since metal is scarce on virtually every map.
Energy is easier to come by.
You have at your disposal solar, wind, geothermal and tidal generators. You can also extract energy from biological elements such as trees on the map, converting the tree into energy. You can store metal and energy for use later, and can build energy and metal storage facilities to increase your capacity. Large units take a lot of metal and energy to create so a solid mining and generating infrastructure is vital to create multiple units at once. Energy is also used to repair units and structures.