Read more: Robert Downey Jr. speaks about Irish blood in his veins

Robert Downey Jr, star of "Sherlock Holmes", "Ironman" and also a reformed drug addict taught Gwyneth Paltrow how to be an addict for her new role in "Country Song".

Downey Jr was arrested on numerous occasions from 1996 through 2003 on drug related charges. In 1999 he explained his drug addiction to a judge in court. He said "It's like I have a loaded gun in my mouth and my finger's on the trigger, and I like the taste of the gunmetal."

In the past he also admitted he had been addicted to drugs from the age of eight. He said his father, who was also an addict, had given the drugs to him.

In "Country Song" Paltrow plays a country star who rises back from that bottom in the new movie.

She said "I just couldn't understand how you could be so drunk that you could wreck people's lives and then wake up the next day and pretend everything was fine," she told Reuters. "I struggled with that."

She explained "I asked Robert, 'How does this work?'...He was really articulate about addiction and the psychology behind it. He really helped me a lot."

Read more: Robert Downey Jr. speaks about Irish blood in his veins