I just posted a Thin Lizzy tune a little while ago but this one is totally worth a listen too.  If you've watched Metal Evolution on VH1 Classic (the very best documentary/series on TV ever) or any other series that references the origins of metal, they like to delve into glam (T. Rex) and then show how that crossed over into metal.  I think that cross-over happened with Thin Lizzy.  This song is the perfect example of their glam-meets-metal sound.  Phil Lynott... what a loss.