Bake paint means that paint job done in a room which is heated at appropriate temp which helps the paint to stick & dry soon - also there is no intereference of dust particle and u just need polishing after paint.
While in normal paint u need cutting using sand paper and then polishing.
For black metallic colour, I will suggest that u should go for bake paint for extra shine and good finishing.
U just need to pay 3K to 4K more for paint booth.....