Thanks to modern technology and the vastness of the internet, many people have started combining songs in all kind of clever ways. These mashups bring lots of joy to us, and we love to pass it on to our listeners, and we don't mind giving a preview of things to come.
And so with that in mind here is an excellent mashup of Iron Maiden and The Monkees by the very talented DJ Schmolli - The Trooper Believer.
You can find more mashups of his at http://djschmolli.wordpress.com/, AudioPorn Central and http://www.mashup-industries.com/. I also suggest exploring these sites further as there is tons of free music floating around, just waiting to be grabbed and sucked through your ears.