want to install new led lights but they have aluminum wires , can i join to copper wiring with merrits?
Although I doubt you have aluminum wiring in a new device (probably tinned copper).
You can join aluminum wire to copper wire with alumiconns. These are special wire nuts that have a special jell inside and these are 1 use only (alumiconns are usually purple or the 2 brands I have used are purple) for example the box I have on the shelf is ideal brand Twister AL/CU, these are listed for aluminum to copper wire connections. Regular wire nuts create a fire hazard with copper to aluminum connections so it can or needs to be done with alumiconns.
I would bet you have tinned stranded wire coming from the new fixture. If you take a knife and scrape the wires there will s probably copper under the tin. If copper under the tin you can just use a standard wire it that is the correct size for the wire.