Hey, GuardianFan, welcome aboard!
Do see the chronology thread that Phil linked to, but note that Machine Man #18 and Uncanny #139-140 are canonically concurrent. In one of the issues, somebody actually says 'the other characters aren't with us right now because they're guest-starring in the other comic'...
Um... maybe not in those exact words...
It is winter!
I think that was on my Marvel Premiere Classics thread where I said that. Might've been both.
~ Le Messor (Mik)
"I have come to the conclusion that there is nothing good that doesn't have bad consequences and nothing bad that doesn't have good consequences."
~ Pete Seeger