You will probably not return to read this but I will say it any way.
Why on earth would you bother with a radio station or show that plays tunes these days?
I mean seriously, you live in the internet era, you know what's going on around you - why then bother with such an antiquated concept?
Here's the low down: any one of us can get on a site like pandora and program exactly the genre of metal and the band we want to listen to. Then of course there is youtube which allows you to pretty much find anything you want to sample without having to wait and hope that maybe something you'll like will pop up in your playlist.
I am not against radio stations or shows devoted to metal but the concept of tuning into a station to listen to my favorite songs is so dated - it's so pre-internet era.
If your target audience is metalheads, then I can't fathom many tuning into a radio station just to hear a bunch of their favorite songs or hope to find something new to listen to. Reality is, metalheads are collectors and will already have most of everything you're playing - and if they don't have something then it's likely they don't listen to that band.
As for finding out new bands, again Pandora-like services are great for that and sites like blabbermouth, no life til metal, forums etc provide sufficient information for anyone interested in either discovering new bands or keeping up to date with their current favorites.
There is very little point in putting the effort of a radio show dedicated to metal nowadays. I would encourage you to think of a different format - run features on bands and have a talk show - invite musicians and music journalists and talk about a band's albums, history etc.
Give us something interesting to cling onto rather than just throwing together a bunch of songs you want us to listen to.
Like it or not - welcome to the 21s century.