Metal, Metal, Metal. Whatever you choose, make sure it has a metal container, a metal housing on the feeder, a metal funnel, a metal slinger plate. I have a Kenco brand feeder that has a cast aluminum housing mounted under a metal 55 gallon drum. The drum stands on three galv. steel legs which are butted into three steel "leg stubs". The leg stubs are a kit made by Moultrie, bought the kit at Wal-Mart for $20.00. I have two other feeders (3 in all). One is a "Tornado" by Kenco, metal legs but plastic container (patched several times). It has three motors that are straight shooters. I leave all three motors"on" because two always seem to be jammed

Requires 2 6v batteries.
The third feeder is a 55 gallon drum, same set up as #1 above except I have an inexpensive Moultrie feeder bolted underneath. I've replaced the plastic funnel with a steel one and the plastic slinger plate, well its still plastic. I'm on my third plate because the critters chew em' up causing all 350 pounds of corn to pour out of the drum. Bummer.
The Moultrie has a photo sensor so it feeds once in morning and once about an hour before dark but it has "smarts". After it spins it shuts itself off for 7 hours, so lightning won't empty your drum. A top quality alkaline 6v battery (silver & blk) lasts a year.