Let’s start with the classic four. In most second-world fantasy I’ve read, dragons linked to fire, water, earth, and air are basically the building blocks. But writers often layer in more interesting details beyond just breathing the element. A fire dragon’s scales might retain heat and glow like embers after a fight, or its lair could be a geothermal vent system. Earth dragons aren't just about rocks; they can cause localized tremors or have a hide that looks like moss-covered stone, blending into mountainsides. Water types might control mist and tides, not just spout water, and air dragons could manipulate pressure, creating silent vacuums or deafening sonic booms with their wingbeats. The best depictions make the element part of their biology and behavior, not just an attack.
Recently, I've seen authors get creative with combining elements or subverting them. A 'volcanic' dragon that controls both fire and earth, spewing magma, or a 'storm' dragon merging air and water for hurricanes. There's also a trend toward more passive or environmental powers—a forest dragon whose breath encourages rapid plant growth, or a crystal dragon that geomantically shapes rare minerals. It moves away from pure destruction. Honestly, the elemental system often reflects the magic worldbuilding of the setting; if the novel has a rigid four-element magic system, the dragons usually conform. If the magic is softer, their abilities get more unique and metaphorical.
What really defines them for me, though, is how their power ties to the plot. An earth dragon guarding a sacred mountain pass isn't just a monster with rock armor; its power to seal tunnels or cause landslides becomes a geographical obstacle the characters have to cleverly navigate, not just fight through. That integration is what makes them feel mythic rather than just a fancy spellcaster with wings.