I often have clients who ask what kind of range hood should they get for their home. Here's some general guidelines regarding residential kitchens (completely different rules apply to commercial kitchens and I do not address them here (there - now my lawyers are happy).
What does a metal range hood do for me?
1) They provide a metal fire shield between the stove and the cabinetry
2) They provide a light directly over the cooking surface
3) If vented properly and are of sufficient power they can readily collect cooking grease from the air and expel odors from the house thus making your house smell better and keeping the grease from landing on the cabinets, floor, and counters