He’s the one with weight of the universe on his shoulders. During the war of the TITANS, ATLAS stormed Mount OLYMPUS and threatened the rival Olympian Gods. As punishment for this war crime, ZEUS sentenced him to hold up the heavens and bear their weight on his shoulders forever.
Now the heavens might be made mostly of cloud, but you’d be surprised how heavy they are. (In fact it’s a miracle they managed to stay up so long before ATLAS showed up.) So ATLAS was very relieved when the laboring HERACLES came along offering to give him a hand in return for a little help with some Golden Apples from the HESPERIDES.
ATLAS nipped off to get the apples but wasn’t inclined to resume his burden. "Here, hold this a minute while I scratch my back," said HERACLES. And ATLAS, not the brightest apple in the barrel, did so while HERACLES made a sharp exit.
ATLAS is usually depicted as a strong silent type carrying a globeon his shoulders. (Well, it’s easier to draw than the heavens.)
Just for the record, he is the son of CLYMENE and IAPETUS. You may be surprised to learn that he is also the father of several children, including the PLEIADES, HYADES and CALYPSO. His girlfriend PLEIONE manages to keep it all together while he is away.