Recommended
EEVblog #42 - Exploding Capacitors in High Speed
Why people recommend it
An older EEVblog video blowing up electrolytic capacitors, linked to show what happens when polarity is reversed and why it matters for safety.
Watch for: Entertainment with a lesson; do not repeat without eye protection
In their words
As usual, you need look no further than the eevblog exploding capacitors video
scld on electronics.stackexchange.com, Dec 2013. CC BY-SA.
Connecting positive and negative incorrectly will also result in failure, often dramatically.
JYelton on electronics.stackexchange.com, Apr 2019. CC BY-SA.