How can Astro be so powerful?

[Thylacine 2000]

Astroboy is made of metal, he's got all sorts of weapons systems inside him, and he's strong and dense enough to be able to lift super-heavy objects, give beatdowns to enemies many times his size, and even survive atmospheric re-entry.

Yet we were told in the new series that he only weighs about 30kg (~60lbs).

Even in the context of a fictional story.... how can he be so strong and dense and at the same time so lightweight? I always assumed he was more like 500 lbs. He just carried it well.