I always thought ‘Barracuda’ sounded a bit more Iron Maiden-esque than thrash metal. :P But then, Maiden, while not thrash themselves, were a huge influence on that genre, so again, evolution…
*BTW: If you really want to hear where Maiden got their sound there’s Genesis (back when Peter Gabriel fronted the band and Phil Collins kept his ass behind the drum kit) and Arthur Brown (you can probably tell from even that short clip how Arthur Brown has influenced, directly or indirectly, countless rock/metal acts of the proceeding decades).