No. It's Venom who started that trend and who is the most cited. MF don't really have a Black Metal aesthetic to them at all (which is a more stripped down sound with hints of punk).
I already said that Venom were largely the ones who started the trend. Selective reading much?
And MF don't have to actually BE a black metal band themselves to have influence on the genre. If I said otherwise, then I'm wrong, but I don't think I did.
As for the similarities in Venom's sound they're there.
The only similarities are that they're both metal bands and they both write lyrics about Satan. That's about as far as it goes.
The punk influence in Venom's music is so apparent that I dont know how you could miss it.
Mercyful Fate sounds far more thrash than Black Metal (excluding lyrical content which is really the least important part of the Black Metal sound).
Which songs? Granted, they played some fast tunes, but I would never consider them thrash.
I think I should just stop this discussion right now because I've just remembered that you're impossible to convince of any view you don't already hold. The punk influence in Venom's music is irrelevant to the sound. Mercyful Fate's music is not of the blazing speed thrash variety but is well within the genres normal conventions. I mean Satan's Fall is a thrash song with lyrics about satan. I don't know how you think that isn't a thrash song.