Why is the system unit cracking and current flowing through the case?

Question

Power Supply

Not long ago I connected an LED strip to the computer power supply. During the connection, one of the bare wires touched the case, a spark went out, and the computer went out.
What does this mean? it's bad that some kind of charge is walking around the case. can something happen to the PC? as it is powerful and it will be a pity if that.
And more recently I hear rustles from the system unit, they appear when, for example, in the browser I point to a link or move the mouse. What is it?
I would ask for help with the SOLUTION of the problem and not advice on buying a new power supply.

Answer 1

Check the PSU output voltage (5/12V), open the PSU and visually look for swollen/leaking capacitors.