Making the Guinness Book of World Records in 1975 as the worlds loudest band, Deep Purple, was at the fore front of the Heavy Metal/Hard Rock music wave from the early 70's.  Fireball is their 5th studio album, released in 1971, and certainly one for the collection!
Here is Strange Kind of Woman:

Following Fireball, with perhaps their best album; Machine Head was certainly their most commercially successful, going double platinum in the US!  Of course everyone knows Smoke on the Water, the source of my favourite misheard lyrics "slow moving Walter, fire engine guy"; but this album has much more than that for your hard rockers! Give a listen to Highway Star:

If you are a fan of this band at all, then this is an essential album for your collection.  Deep Purple resisted releasing a live album, feeling that they could never replicate on vinyl the power of their live performance.  But in order to compete with the flood of bootlegs being produce, Made in Japan was recorded over a three night period at live concerts in, you guessed it! Japan.  This album comes as close as you could to being there.  This was the era of long live songs, as recorded here with Space Truckin' at just over 20 minutes!  This was the first album I bought.  Not the first in my collection, I was given some as gifts before this, but this is the first I saved for and bought myself.  Considering my first stereo was not all that great, this is still in fairly good condition; and I played it a lot then! I won't subject you to the 20 minute version of Space Truckin', but here is Lazy at half that: