On a tour maybe... in the stupid not a chance in hell. Those guys are gear junkies. They may not know how to wire up their refrigerator sized touring rigs (which is why you hire someone so its done right), but they know their stuff.
Also guitarmaster, who's to say a pro can't use a behringer or line 6 gear? The whole boutique, high end, analog pedal is better than anything digital or mass produced out of china arguement is so stupid and juvenile. Take a player like Dave Navarro... the guy has awesome tone and achieves it with stock Boss pedals into a JCM900 set clean. No special boutique amp, no special boutique analog pedals, just a guy who knows how to use his gear to get a good tone.
As for Metallica, those guys have been tearing it up for 25+ years now and have crafted some of the best heavy guitar tones in their tenure (Master of Puppets, Black Album, the Load sessions)... they must be doing something right tonewise to garner that type of respect out of the musician/guitarist communities.