tuning "e" to "d"

by paul
(montverde, fla, 34756)

i am kinda new to playing the electric guitar,,a friend of mine who also plays, but not really metal,says you can tune the bottom "e" string down to "d" and it gives you a more heavier, metal crunch sound, which i have and which it does, my question is this a common thing that guitar players do that play that style of music or am i starting off on the wrong foot, i dont want to develop any bad habbits starting off,, thank you,,, paul