There are pretty much no heavy metal FM radio stations. You'll need to listen to freeform radio. I actually host a metal show on Mondays from 8pm-10pm EST on my campus radio station. There's another metal show at the station and he's on RIGHT NOW AS I'M TYPING THIS 9pm-midnight on Sundays.
The summer schedule isn't up yet, but here is the station's website: www.wmucradio.com
You can stream the broadcast live from that website, so you don't even need to be in the College Park area to listen.