I love metal but also admit that my taste in metal I listen to day-to-day is terrible. Attempting to avoid my own bad taste, I'd recommend a few of the bands already mentioned, but would add in Alter Bridge, who I've been into recently. Bands like Iron Maiden, Black Sabbath, Metallica etc. are obvious suggestions that I'd hope you've already heard are some point. I'm gonna take a risk and throw Five Finger Death Punch in there, 'cause I love them no matter how generic they can be. Trivium and In Flames are great too.