Axl Rose is an icon. He scream-sings some of the biggest metal hits from the 1980s and early 1990s. Songs his band, Guns N' Roses, produced on albums such as Appetite for Destruction and the Use Your Illusion records. While Slash and the rest of the band were great, there is simply no GNR without Rose's bombastic showmanship and vocals.
In 2016, though, after AC/DC frontman Brian Johnson could not perform due to some health concerns, Rose filled in on 22 dates. He did not try to be Johnson, even though the two are not dissimilar in terms of vocal technique. After all the success Rose had, he earned the right to be himself.
Plus, being Axl meant the music was sincere instead of him trying to mimic Johnson or Bon Scott. Rose was also respectful of the rest of the band and let Angus Young take front and center on stage instead of the singer trying to stand out. This was how it should be. After all, AC/DC belongs to Young, and Rose was just helping out.
AC/DC had one rule for Axl Rose when he helped the band out in 2016
According to the band's touring drummer at the time, Chris Slade, AC/DC and the band's management had one rule for Rose during the run of dates he did with the band: Don't misbehave. Rose was there to help, and if he could not do that then the band could look elsewhere for a temporary singer.
Slade told the Road to Rock podcast, "With AC/DC, (Rose) was sent to boot camp. (he was told if) 'you screw up, Axl, you’ll get the boot.'" To be fair, Slade said that Rose was not a concern at all and handled himself with class.
Slade also said, "(H)e did a great job – tremendous job. He’s not (Johnson), and he wasn’t trying to be Brian, and he also was not trying to be Bon. He’s got a lot of respect for Bon Scott."
By most accounts of those fans who saw the shows, Rose and the band performed well. The credit for this should go to both AC/DC - who after 50 years knows how to run the band efficiently and smoothly - and also Rose. The singer knew his role and accepted that. He has a legendary ego, but he set that aside to help the hard rock icons.