Swedish metal band In Flames guitarist Björn Gelotte was interviewed by Music Radar, and he explained why every guitarist should learn how to play drums. 

He says:

“Playing drums really helps your songwriting; you get an understanding of dynamics and arrangement. It’s a lot of work physically – you learn not to overdo things. The drums don’t need to be in the foreground; they should be very much the foundation of the song. I’d say it helped me more than actual guitar playing, because I’m a lazy fucker!

In the some of past interviews, Eric Johnson was talked about something like that. According to his claim, every guitarist should play basically piano. 

Click here, if you want to read all interview with Björn Gelotte.