I've pondered for some while having a dragon somehow get accidentally teleported into the modern world and the only thing he can find to fuel his fire is batteries and lightbulbs.

Maybe others eat phoenixes or have them living in their mouths like crocodile birds.

Having a phoenix make its home in a dragon's mouth (or in a dragon statue [I might use the latter, but not likely the former]) would be fascinating. Or a swarm of fireflies that are literal fire.

In my webcomic setting younger dragons, roughly the size of horses eat pretty much any meat they can catch, adult dragons, now as big as a house tend to hunt bigger prey such as bears, elephants and other large creatures but start to act more like say pythons or anacondas and after eating a big meal say a few hundred pounds of of whatever meat they can find tend to not eat again for months and usually sleep for weeks while the oldest and biggest dragons grow about as large as a commercial airplane and they must hunt and eat things like other dragons, whales and giants and then once full tend to sleep for decades at a time only waking up between decades to eat again, build up its hoard of shiny objects or mate.

Huge creatures can be a real strain on their environment so I thought this system would be a fun kind of real life quirk to add to a fantasy element.

Sorry for talking so much, God bless!

My dragon eats soldiers and their murdered families.

Maybe others eat phoenixes or have them living in their mouths like crocodile birds.

In one of my NaNos, my dragons (along with other fire-related creatures) eat the berries of a type of tree (which really should have a name, but hey, it was NaNo and it took up more words to say "the spindly fire berry tree with leaves of orange" than "Flamebush" ) which give them certain nutrients and chemicals necessary for their flaming. The story actually focused on a disease which affected the tree and started killing the fire-creatures. The phoenixes in that story ate the fire berries alone, but the dragons would eat anything that tickled their tastebuds.

There may be sentient dragons who eat stupid or witless dragons, believing themselves to be the superior race worthy of such domination.

I wonder if fairytale dragons always want maidens because maidens have a higher fat content than knights.

I extremely doubt that's the case...

Not only would it be easier to take the maiden (I mean, the knight's just gonna kill him) but she also won't be wearing as much armor (if you're a dragon, do you seriously want armor stuck in your teeth?).

Now I'm thinking about writing a fairytale in which the knight goes undercover as a lady in distress so he can kill the dragon.

Dooo eeet.