My mother does like some of the bands i listen to, she loves Opeth accoustic parts, love the Ulver accoustic album (made me do a tapes of it for her to listen at work). She is not into growl much, she loves Rapsodhy (i once was doig my homework when i heard her singing along the music on Raphsody). I often get the comments : "The music is great but the growls are a little too much for me".
She loves Dream Theater especially their last album, she like the Malmsteen concerto CD...
She knows a lot of band by names and by sound, i even mentioned Gorgoroth one time and she knew them.
But the biggest thing that happened to me was while we were in a car with some friends of mine (metal fans), she was driving, and i put a tape, i said : "Let's listen to some Immortal"
The music started (it was not Immortal but Mayhem), after 15 seconds she told us : "It does not sound like Immortal, isn't it some Mayhem, son ?"
You should have seen the look on my face and the look of my friends faces... It was priceless