"Iron Man" star Robert Downey Jr. is known as one of the world's highest-paid actors. He is also said to be one of the best of his generation.

In GQ's feature, the "Avengers" star talked about "Iron Man" and what his younger self would think about the film. Downey Jr. also gave his advice to young actors aiming to achieve his level of success.

"Well, first of all, back then, the reference would have been Christopher Reeve. And Michael Keaton," he said. "So I'd have been somewhere in the middle of either having a judgment on it or saying, 'All right, cool people are doing it.' But I know that I must have read those comics before, or they were in the atmosphere."

"If you always talk about all the cool stuff you're gonna do, and you don't understand why it hasn't already happened for you, because, you know [snaps fingers]," he added. "The fumes of that will get you over the first hurdle, and nothing else. You must learn to put your nose to the grindstone for years and not look up, no matter how much rejection is heaped on you."

When asked on which movie set he had the most fun, Robert Downey Jr. admitted that his movies with Marvel were great. He also enjoyed 2008 action comedy film "Tropic Thunder."

"The first 'Iron Man' was great. Third 'Iron Man' was great," the actor told the publication. "As a matter of fact, you know what? 'Captain America: Civil War' was a blast."

"[On 'Civil War'] we happened to be, by our own volition, shooting on what must have been one of the three hottest tarmacs in the history of North America, all suited up, just going, 'This is crazy! We shouldn't be outside!' And there was something so funny about it."

"Captain America: Civil War" effects supervisor Dan DeLeeuw told The Wrap about how Robert Downey Jr. worked twice as hard for the part where Tony Stark's younger and older self were in one frame. "It's even more difficult watching him do it," he added.