IMO early punk was just fast rock 'n roll, it influenced by Glam as well, which came a few years earlier, the second wave with the likes of Exploited was a lot more shouty shouty and the American hard core, Black Flag Bad Brains, even more so which I don't like much.
So you've got the melodic punk, which the early stuff was, Ramones, Clash, Sex Pistols, Undertones Buzzcocks etc and then later on Green Day, and even Blink 182, then the shouty shouty hard core, really they're two completely different things, well I think so anyway