This little soldier isn't dealt a good hand in life. He's different from the other tin soldiers in his set because he's missing a leg: He had been the last one to be cast and there had not been enough tin" (12.2). Hopefully, you future parents out there don't run out of human-making materials anytime soon. But luckily, our little tough guy is tough, so "he stood as firm and steadfast on his one leg as the others did on their two" (12.2).
Maybe he was taking some lessons from a flamingo.
The little tin soldier isn't just steady in the physical sense, though. He's also unflappable. When he's pushed out the window by a jealous jack-in-the-box, he gets sucked down a gutter and into an underground stream. Despite this trauma, "The poor tin soldier stood as steady as ever, he did not flinch" (8.18). We gotta give it to him: he's brave in the face of adversity. Like most good soldiers, we imagine.
And our little guy gets a pretty happy ending. When he finally makes it back to the household where he lives, he gets to be with the cut-out ballerina he's fallen in love with. When he sees that she's still standing there after all his time away, "he almost cried tin tears—and would have, had it not been so undignified" (8.23). Because soldiers don't cry, apparently. And neither do human boys or big girls. So maybe this tin soldier is a tad repressed, but he's in good company, and we admire his bravery nonetheless.
Why does the soldier fall in love with the ballerina? When he first sees her, he notices: "She stood on one leg, and at that on her toes, for she was a ballet dancer; the other, she held up behind her, in such a way that it disappeared under her skirt; and therefore the soldier thought that she was one-legged like himself" (12.3).
First, that must be one seriously talented ballerina, or one epically rockin' optical illusion. Or maybe the tin soldier's eyes are also made of tin, and therefore he doesn't see very well. Nonetheless, he falls in love with the ballerina based on a misunderstanding that they share this one-leggedness.
The tin dude and the dancing dudette never actually speak to each other. This silence makes us kinda wonder what the actual basis for their relationship is. Maybe Andersen's trying to teach us a lesson here: it's easy to fall in love with someone from afar, as we pine for the perfect image of a likely imperfect real person. And it's especially easy to crush on someone whom you share some superficial similarities with. Who wants to eat Swedish fish and watch Doctor Who with us? Okay, great, let's get married.
When a boy chucks the soldier into a stove, it's the end for him. His paint begins to melt off, and he knows he won't last long. However, he maintains eye contact with the ballerina even during his final, goopy moments: "He could feel that he was melting; but he held on as steadfastly as ever to his gun and kept his gaze on the little ballerina in front of the castle" (12.25).
But then a breeze floats the paper ballerina into the stove with him, and they perish together. Which is rather Romeo and Juliet, don't you agree? All that's left of him is "a little tin heart" (12.26), which symbolizes his faithfulness toward the ballerina even in the face of death.
Alright, alright, we get it: the tin soldier is steady, brave, and true. Even if he only loves the ballerina because she's steady on a single leg, he sure pot-committed to that love.