Assuming you meant space themed, as in songs about space or being in outer space......
Iron Maiden - Space Station No. 5 - YouTube (cover of Montrose song, but better)
More in the rock genre, but there are probably metal covers somewhere of these:
Major Tom (coming home) - Peter Schilling
Space Oddity - David Bowie
Why Me - Planet P (my favorite as it reminds me of my childhood when MTV played music)
Planet P Project - Why Me - YouTube
If you meant "Space rock", as in the genre, like the way SomeBadDrummer interpreted it, then anything by Ozric Tentacles.