The 'For Your Entertainment' hitmaker credits the 58-year-old music mogul - who menotred him during his time as a contestant on 'American Idol' in 2009 - always telling him exactly what he thinks with enabling him to face the ''brutal'' showbiz world.
Adam told The Sun newspaper's Bizarre column: ''Simon really supported me, he was amazing.
''I mean, he even gave me the tough love that I needed as well. Simon is known as Mr Nasty, he is the guy that is going to tell you the truth.
''He wants to see if you can hang as an artist, as this industry is brutal, and the public is even worse.''
Adam - who now fronts iconic rock band Queen in place of the late great frontman Freddie Mercury - hasn't been in constant communication with Simon, but he dropped him a compliment when they saw each other on 'The X Factor' in 2016, when the singer performed with finalist Saara Aalto.
He recently said: ''I bumped into him when I did 'The X Factor'. I did the finale the year before last, and it was the first time I had seen him in 10 years. He was sweet. He said, 'Good to see you - good job.'''
Meanwhile, Adam recently admitted he joined Queen because they felt like a ''safe space''.
The 36-year-old singer has been performing vocals for the 'Bohemian Rhapsody' group on tour since 2012, and he took the decision to go out on the road with the British rockers because of the criticism he was receiving for his flamboyant persona.
He explained: ''I needed an outlet for me that wasn't judging. I needed to be in a safe space that didn't say to me: 'Don't do that, people won't like that.'
''Now there's an audience for me being exactly who I am. There's permission given.''
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