More into 70s hard rock than metal, but I'll post a few songs I like.

https://www.youtube.com/watch?v=xkkpUEAraYA
~1977 - Cirith Ungol - Last Laugh

An old, unreleased demo from California doom metal pioneers Cirith Ungol. Although it definitely wears its 70s glam rock influences on its sleeve, it definitely hints at the music they'd eventually make.

https://www.youtube.com/watch?v=ouClIX_Dxl8
1978 - Sorcery - Arachnid

This song isn't good, but I love it. It sounds like a bunch of late 70s nerds singing about their Dungeons and Dragons campaign in their basement. The lyrics are just fantasy madlibs - "lead our king, whose mystical forces noone dares to know."

https://www.youtube.com/watch?v=j4x1i66FyoA
1979 - Praying Mantis - Captured City

Extremely catchy NWoBHM from a band that would later drop metal and veer more into AOR.

https://www.youtube.com/watch?v=Nspf_t41bF8
1979 - Triarchy - Save the Khan

Something that I love about early NWoBHM is that it's not just influenced by metal. The intro comes from Devo's Mongoloid; I love the weak, wobbly synth lead. I also love the lyrics; they're so much more poetic and thoughtful than most metal. I feel like this song really meant something to the guy who wrote it.

https://www.youtube.com/watch?v=zowid7KAmnM
1980 - Bleak House - Rainbow Warrior

Another example of non-metal influence. The main riff definitely borrows from The Strawbs' 1973 Down By the Sea, but they do something so new and interesting with it.

https://www.youtube.com/watch?v=VDv9le4Km3M
1980 - Race Against Time - Bedtime

Heavy and brutal NWoBHM. There are a couple versions of this song, one from 1979. This version appeared on the New Electric Warriors compilation tape, which played a big part in the spread of the NWoBHM movement. The band later evolved into Hell.

>>126893345
I'm going to take the opportunity to post some very heavy hard rock and early metal. I'll post it chronologically. Hope you enjoy!

https://www.youtube.com/watch?v=orPrRGRWEHc
1971 - Bag - Nothing Will Remain

Interesting psychedelic band from the Netherlands with very little output.

https://www.youtube.com/watch?v=gURiVS2cpJg
1972 - Jerusalem - Primitive Man

Caveman music produced by Deep Purple's Ian Gillan. Really fun - there are times when it feels like it skipped the 70s and 80s and went straight to the 90s.

https://www.youtube.com/watch?v=-TUkxrrDiUc
1972 - Ruja - Tütarlaps Kloaagis

I simply cannot explain this song. Bizarre, experimental, depressing and heavy. Apparently this was a pretty big band in Estonia, but I kind of doubt this was one of their hits.

https://www.youtube.com/watch?v=l-HCh7JMQ3g
1973 - Blast - Damned Flame

Hesitant to post this one because it kind of sucks, but it's got a massive energy and heaviness for the era. Fascinating, but not very listenable.

https://www.youtube.com/watch?v=zKS5Tw7mlk4
1974 - Pentagram - 20 Buck Spin

Most people here probably know Pentagram and what Bobby Liebling went on to do in the 80s. This is a 1974 recording of one of their classic 80s songs; a rendition from as early as 1971 exists in the form of "Crucified". Part of what makes this song so heavy is that the bassist, Greg Mayne, is playing chords.

https://www.youtube.com/watch?v=Qa4TlPfYcDs
1974 - The Groundhogs - Sad Go Round

A slow, heavy song from the Groundhogs' seventh album. The band was fairly big in Britain, but this album didn't make much of a dent in the charts. Maybe the novelty of heaviness was wearing off.

https://www.youtube.com/watch?v=jQGUr-Zs6Fo
1975 - Pure Hell - Wild One

All-black punk band from Detroit recording very heavy and ominous music for the era. They would later rerecord it in much higher fidelity in the late 70s.