Hellfest
In short
An annual heavy metal music festival held every June in Clisson, France. It is one of the largest metal events in Europe and the most successful music festival in France by turnover.
In plain words
It is a massive outdoor party for fans of loud, heavy music. Thousands of people travel to a small French town to see many different metal bands play on big stages.
A simple example
A fan might buy a multi-day pass to watch various bands ranging from thrash metal to black metal over a long weekend.
Why it matters
It provides a major global platform for extreme music genres. Its huge scale makes it a key event for the international metal touring industry.
Easy to mix up
Do not confuse it with Wacken Open Air, which is a similar large-scale metal festival held in Germany.