Probably the first song with a recognizable hardrock/metal sound: Cream with "Sunshine of your love" (november '67)
http://www.youtube.com/watch?v=FI8SUc2SV4k
and Blue Cheer probably released the first Metal album
(Vincebus Eruptus, january '68 )
http://www.youtube.com/watch?v=t-kFe4l_W30