Fans
If your stage gets to a point where it needs repairing, you need a certain number of fans. This amount varies depending on how much damage has been done to your stage. In "Brutal Legend," fans act as resources do in other real-time strategy games, such as Vespene Gas in the "StarCraft" series.
Fan Geysers
To get fans, you need to set up a Merch Booth on a neutral fan geyser. These are spread out over the battlefield, and the neutral ones glow green. To build a Merch Booth, stand near a geyser and play the Fan Tribute solo. This is accessed via the solos menu, which you can pull up by pressing "R1." Select the Fan Tribute solo from the solo wheel, then press the displayed buttons to play the song. The Merch Booth will be built automatically and you will accumulate fans.
Defending the Stage
A strong defense is tantamount to victory in "Brutal Legend." Any units you recruit can be positioned around the stage to prevent further damage if you get overwhelmed by enemy units. If your stage is in mortal danger, send some units to the stage to distract your enemies before you start repairing it to give yourself some extra time.
Repair the Stage
Once you've got the necessary resources and a strong defense, hop onto your stage and press "Triangle" or "Y" for the PlayStation 3 and Xbox 360, respectively. This will pull up a list of options. Select the "Repair Stage" option to spend your fans and repair the damage done to your stage.