Helter Skelter by The Beatles is probably the best way to ease yourself into Heavy Metal since it kinda influenced its creation. Some Led Zeppelin stuff is kinda good to ease into too, and then go onto Black Sabbath and then go from there I guess??
I don't really know about properly modern heavy metal, especially since these days there's just so many subgenres of it all but if you just want like, your basic metal and whatnot go with that. Throw in some Metallica as well (Garage Inc. is probs a not bad way to give them a try since it has covers and might be a little easier to get into) and some early Iron Maiden too
then again I'm no Metal expert, I just like certain bits here and there. Again though, if it's just not your cup of tea don't try and force yourself to like it to fit in ^^;
np: Nik Kershaw - I Won't Let The Sun Go Down On Me [Human Racing]