This one surprised and delighted me. Weightless is one of those films that some will get nothing from and others might says its too on the nose.. I would disagree with both and says its quite subtle and meaningful. Its also one of those films where some would argue, "nothing happens".. Or, "its slow and boring". Well the idea that nothing happens isn't really accurate but I also don't think its completely false either, at least regarding the father son relationship in the beginning. The movie starts with the father and son and their non existent relationship and in a relationship that doesn't yet exist, not much can happen, can it? It takes time which is reflected as a slow burn of an experience.
The boy and his friend talk about the super hero powers they wish they could have, the boy says he wish he could be invisible. Earlier we see him with a paper bag over his head, he isn't happy with his weight and the way others see him. Later we see him shirtless and covered in animal stickers.
Throughout the film we see a goldfish in a bowl, much like the characters, the fish doesn't have much to do and not many places to go. For the boys birthday we see he has gotten a store bought cake with a decorative spider on it (spider man is supposedly his favorite superhero). The cake still has the plastic cover on it, almost replicating the fish in the bowl.
There's a lot more symbolism here that I won't get into as I don't think it needs to be explained to death but can be picked up if one cares enough to look. One of the rare movies that gave me the urge to watch it again as soon as it was over.