Your beer may taste like green apples (maybe cidery) if it's still, for lack of a better word, "green." Let it age a bit and that flavor will probably go away, leaving a wonderfully tasting beer.
Don't worry about it....Open one again in 3 weeks and it'll be fine...
Here's some threads with great info for new brewers and Mr beer users. You'll find the answer to why your beer taste funny right now...and why it'll be better in a few weeks.