I have unused live electrical wires coming out of wall in kitchen where new cabinets are going. How should I handle this?
Assuming you don't want to/can't remove them completely, (i.e.- back to an existing junction box, or all the way back to the breaker box), you need to properly terminate them (capped with wire nuts) in an accessible junction box.
In other words- install a junction box in, put wire nuts on the wires, install your cabinets, with a hole where the junction box is, and put a cover plate on.
The best way to handle this is to find out where the wires are coming from and terminate them at that box. In most cases this is just undoing a couple of nuts and taking the wire out. If you need to open up a small section of drywall to get the wire out, better to just do it now. Adding a junction box is a lot of work for a half ass job and potential issues and unneeded troubleshooting in the future.
If they are coming directly from your panel I suggest that you disconnect the wires from your panel (label them there - there being outside of the physical panel but in same location) and put the wires sticking out of your wall in an accessible place in your house where you might have future electrical needs (attic or basement). Of course if you do not know how to disconnect from the panel, that is a different question on here.
Note: Another option is moving this to right above cabinet height to allow for the ability to plug in lighting with a basic receptacle - if you don't want to remove the wire. This is $5 and 10 mins.