Sage Mode is one of the best ninjutsu techniques in the Naruto world. Mastering it requires lots of time and effort, but those who put in the work will become one of the most formidable shinobi. Sage Mode takes ninjas with already-impressive chakra reserves and increases them even further, and gives them the power, speed, and durability to keep up with proficient ocular jutsu users, even those with the Mangekyo Sharingan or the Rinnegan. It's what made Naruto Uzumaki the single most powerful ninja in his village and helped him defeat Pain when no one else could.
Source：https://www.cbr.com/naruto-sage-mode-explained/
