Madison Square Garden is a notoriously big venue — it seats almost 21,000 people — so when Mendes took the stage and his many, many enthusiastic fans stood up in applause, the entire room literally shook. Most of the crowd kept on their feet during his set, where he sang his hits in addition to a tasteful cover of "Use Somebody" and swapped out guitars between each take. The sweetest part? He threw his guitar picks into the audience after he finished each song (probably causing unintentional brawls between fans). The best way to sum up the performance is the way a bystander did when asked, "Do you know this song?" "I know all of them," they said. "And I didn't even realize it." - ANGELA WEISS/Getty Images

Shawn Mendes had the whole room shaking