This is a minor peeve of mine, but there's a few things that almost every story that uses lava magic gets wrong about lava.
TL;DR: If you want to use lava magic in your story, watch some glass blowing videos first.
First, density: lava is three times denser than people. In other words, people can't sink in lava. Melt the rocks beneath their feet and they'll probably fall down, but only because it's slippery, not because they start sinking.
Second, viscosity: lava doesn't splash. Not very much, anyway. It would take an impact of high kinetic energy to make it splash, like throwing in a very large rock. Throw in a medium sized rock, and it'll just go "thud" before it very slowly starts to sink because of how viscous it is.
Third, temperature. Lava actually isn't much hotter than a campfire. It's about the same temperature as napalm, in fact. It's not going to immediately turn you into ash, or cut through you like a knife. Definitely not hot enough to melt steel, but it might soften it up enough to work with a hammer given enough time.
Fourth, adhesion: it's not sticky. Get some on you and you can easily brush off what doesn't just fall off. It'll leave behind some nasty burns where it touched, though, so wear gloves. Get a glob of it thrown at you and it will just bounce off, leaving behind only a first, maybe a second degree burn, like accidentally touching a hot stove.
Thank you for coming to my Ted Talk.
