What's wrong with my electromagnet
Steel bolts don't make good magnets.  Soft iron is much better.
With that low number of turns on the coil, you will have to put a LOT of current through it to get any strength out of it.
You have to have insulated wire.  Your coil might be made with varnished copper wire, but it is hard to tell from the picture.
To make that electromagnet strong, you will need a powerful battery.  That does not have to mean high voltage.  It means it has to be able to supply a lot of current.  A 9Volt transistor radio battery would be a poor choice - it has a somewhat high voltage but can't supply much current for very long.  A D cell has only about 1.5V, but it can provide a lot of current.


That coil will probably draw more than 1 ampere of current - I don't think your power supply is up to the job.


Use a soft iron bar (like a big nail.)
Use a thinner wire.
Put more turns of wire in your coil (like, one hundred or more turns.)




I'm going to go into "grouchy old man" mode and tell you to quit looking for stuff on youtube.  It great for watching cat videos or old cartoons.  It kind of sucks at anything that needs good explanations and details.

Try looking for education sites like this one that go into detail, and explain things.