I have to go with any of the first three Sonata Arctica albums, in order of (my) preference these are:
Winterheart's Guild
Silence
Eccliptica
but they are all wonderfully inspiring and totally OTT power metal. You have to smile, sing along and play air guitar to them.
I would also recommend (for the metallists):
Paradise Lost - In Requiem.
Paradise Lost have languished in the wilderness long enough. In Requiem is an absolutely brilliant album and, although it's more death metal than thrash, it rivals Metallica at their best. Follow my link and listen to some. All tracks on In Requiem are superb, but I think Unreachable.mp3 is probably illustrative.
BTW. Thanks Knoxville. I hadn't heard Iron Maidens, but now I am in love. I think taking them all out for a few Belgian beers and then home to bed would be my perfect day.