For all the power that Link has, he is still mortal. As such, he is bound by the limits of his body in many cases. Because of that, he can't do certain things, like lift insanely heavy objects on his own.
However, throughout the course of Legend of Zelda, Link has gotten several items to "assist" with that. Whether it's the Power Glove, Titan's Mitt, or the Silver and Golden Gauntlets, Link always seems to find an item to help him lift incredibly heavy things. Including large boulders, and massive slaps of granite and various other stones.