These kind of questions make me think you should hire a professional.

I would put a wire nut on the ends of the wires. Straighten the wire out with pliers and screw the nut on. Usually yellow or orange wire nuts will fit on a single wire. The small wires below are from an old telephone land line. You can just push them back in the wall. And yes, a plain cover will work.

What is that white wire wrapping around the right edge of the box? It must be put fully in the box so that the plain cover will be tight against it.

thank you all. @mtvhike good catch! i will check it out and am also guessing all i need to do is put a plate and call it a day. the exposed wires look like some sort of data wire.

HI, Just because you don't use it doesn't mean it is not used, it could be feeding other outlets downstream. Check it out.

Good Luck Woodbutcher

@Seabornman The small wires are from security system which is no longer being used and is disconnected. How can I safely tuck away the small wires - can I put them in the electrical box?

No, do not put low voltage wires in the electrical box with 120V wiring.

thank you @dennisgli what are my options then if I no longer need low voltage wire?

Yes, just push the low voltage wires back into the wall cavity. What is that white wire that shows on the right corner of the plastic box?

@seabornman the white wire is the same low voltage wire. please see below. is it not against the code if I just push the low voltage wire back into the wall cavity?

I've reread a few times, but still not sure, can you clarify that you only want to "close the outlet . . because you are no longer using it" meaning the telephone wire that was in the lower left corner and what looks like 18ga wires on the lower right? Or are you also talking about the 120V duplex receptacle because you are putting a kitchen cabinet in front of it or something?

FWIW the "ears" of the receptacle should be held on the face of the drywall, and the drywall appears to not only be cut with too large of gaps around the box, but the box looks pushed too far in which both the latter are improper.

@3onthetree i am going to bring in professional to help me bring the receptacle flush with the drywall. Also, I changed my mind and I will leave the receptacle functional. I was only concerned about that low voltage wire.

@Seabornman thank you!