Oooooh I have some many stories from festivals and concerts. Since I am from Austria some of those are austria-specific, but I'm sure you will still enjoy them

• There was an ad where animals were looking for "Gerti", so we reenacted that but first with "Helga" and then when we found out someone was looking for their friend with the friends name. It worked.
• If people are chanting the band's name, someone will start chanting nonsensical words. Sometimes even a wrong bands name and sometimes others will join in. That's how the crowd started to cheer for Sabaton at the rise against concert
• There are some rules in the pit. The most important one is that if someone falls, you help them up again. Then, if they want out, you help them out. I have seen two scrawny little kids hold up an entire circle pit hold the door style because someone fell in front or them
• On the topic of mosh pits, at one concert I was standing at the edge of the pit and someone fell against me. Totally my own problem, but the guy turned around, started apologizing and then knelt down and kissed my hand. Then after I told him it was ok he offered me to get me up to crowd surf. I took him up on that offer
• When I was on one of the largest music festivals in Austria (Nova Rock) I also camped there and was woken up by someone blasting children's songs
• Hands down the best atmosphere at the same festival was at the late night act, which in this case was EAV, an older band with pretty silly songs

Those are just the things I can think of at the to of my head, but basically, this is the reason I love the metal community

In Germany, you'll get:

- the crowd randomly singing Julia und die Räuber (an old song by a well-known band, partly sung by a little girl)

- conga lines

- Helene-Fischer-singalongs (ugh)

- at least one group in neon-coloured animal onesies

- if you bring sparklers and soap bubble makers, you must share them. Yes, I made soap bubbles for Rammstein. They seemed to like it.

- one of the German festivals is on an old airfield, so people bring their kites to fly.

- if you find lost stuff on the floor, you put it up in a visible spot, so the owner can find it. If it's a wallet, you find the owner and return in (happened to my brother - the finder sent it back to him in a letter from the Netherlands).

- one of the traditional Wacken bands is the local "band" of the voluntary fire fighters. They do not play metal, they play cringy old-fashioned Schlager, and they are wildly popular.

Also, the calls for Helga, I need to add, started in the 80s in Wacken, and subsequently spread to every other metal festival in Europe. Legend has is that a drunk guy was looking for his girlfriend, and the helpful crowd started shouting, too. They're still shouting it today, so we can only assume that Helga still hasn't been found.

Also also, when I was at Nova Rock (ages ago) the ground was covered in wood pieces (in case of rain) so of course the crowd threw them around and had sawdust battles. The bands egged them on.