You know you've come a long way when you see yourself in ink. The Metallica boys have very distinctive features (i.e., James Hetfield's ever changing facial hair, icy stone cold blue eyes, and black wristbands; Kirk Hammett's mole, ample lips, piercings, and curly black hair; Lars Ulrich's elongated forehead and multiple body piercings; Rob Trujillo's long hair, box-like face and refrigerator-shaped body; Jason Newsted's square neck, etc.), making them a field day for cartoonists everywhere. Their personalities are larger than life and their past reeks of alcoholic binges and hazardous accidents, all of which fall prey to illustrators who take the subtlest of flaws and features that make each person unique and emphasize them brilliantly beyond the bounds of imagination. Check out some of these great Metallica caricatures...
I don't think Metallica has actually ever been on the Simpsons, but after seeing this drawing, maybe they should consider it. (For those who can't tell, from left to right, that's Jason Newsted in the green hooded sweatshirt, James Hetfield with one of the necklaces he's famous for wearing, Lars Ulrich in the back with the red jacket, and Kirk Hammett to the far right holding the cigar.)  From Rocktoons.com
I'm not sure of the origins of this piece, but the Metallica stereotypes abound, especially James' signature black wristbands, and Kirk's long, curly hair.
"Alcohollica" is a nickname very becoming of Metallica. Of course, it should be noted that James Hetfield has since been to rehab and given up the bottle, but the group has had a rather long and notable history of alcohol abuse. This picture is a spoof of the cover of Metallica's first album, Kill 'Em All.
This cartoon is pretty much self explanatory. It shows Lars' affinity to strip down to his skivvies at every Metallica show. But wait, there's only three of them... Oh my god! They killed Jason! (Sorry, couldn't resist. But I do think Rob Trujillo would make a good "Butters.")
UPDATE: Metallica (James, Lars, Kirk, and Rob) were actually spoofed on an episode of South Park which aired 10/29/03
UPDATED UPDATE: Quit reading this and look further down the page....
A touching tribute to Cliff Burton, the band's former bassist who was killed in a 1986 bus accident. A caption reads (in James' words): "What band? There is no band at the moment... just three guys." Cartoon by "Jerryteacup"
Another cartoon by "Jerryteacup," showing drummer Lars Ulrich mesmerized by a washing machine. A caption reads: "...Lars, on the other hand had got his machine to work and was now sat in front of it, transfixed by the constant spinning of his clothes. Even James waving his hand in front of his face had no effect. 'It just keeps spinning' Lars whispered, fascinated. 'Yeah, yeah, yeah, Lars... Go look at the pretty washing machine.' Kirk comforted, wondered if perhaps the granny had given Lars some brain damage... then he realised [sic] Lars was always like that... -The Stain That Should Not Be-"  

(Poor Lars. Lars is such a cutie pie. People shouldn't pick on Lars so much.)
'Nough said. From left to right, ample-lipped Kirk Hammett, Jason Newsted with his box-like face and neck, James Hetfield with one of his classic sh-t eating grins, and last but not least, Lars Ulrich with his larger-than-life forehead.
My, my, the boys must be going somewhere special tonight, being all dressed up and all. Check out James' skull ring (which once belonged to former bassist Cliff Burton) and Kirk's chin piercing. Regretfully, I'm not sure who created this, but it's one of my personal favorites!
This is one of the designs that went on the t-shirts for the Summer Sanitarium 2003 tour. There's James up top, followed by Rob, then Kirk, and there's Lars at the very bottom. Gee, I wonder how they got their heads through those skinny little bars!
This is the cutest little caricature of James Hetfield I've ever seen. He's just cute as a button -- just like in real life! (Are buttons really that cute?) From Rocktoons.com
Original artwork by artist Fixxxed, entitled "Metallica." Fixxxed is a female artist who creates Metallica based artwork exclusively. Why waste your time and tallent on painting sunsets and the ocean when you've got 'Tallica, baby!  
On October 29, 2003, Metallica got slapped by the South Park fairy as the boys showed their love and support for Stan and Kyle's band: Moop. The episode was a spoof of the controversy over the RIAA suing a 12-year-old girl for downloading MP3 files off the internet (umm.... hmmm) and who better to throw into the mix than Metallica. Pictured here is James, Rob, Lars, and Kirk's shoulder (sorry, Kirk).