I have a 2010 kymco downtown 300i there a light on the dash says mett in and its lit up

They are usually an inline fuse on the wire behind it.

You could ask them direct, or google
make model manual
or
make model wiring diagram
or
make model accessory socket fuse

https://www.kymcohealthcare.com/?q=products

I did find this which has the answer!

12v power outlet fuse - KymcoForum.com

https://www.kymcoforum.com > ...

Mar. 5, 2016 - KymcoForum.com »; Scooters - 125 to 300 »; Downtown 300 »; 12v power outlet fuse ... I blew the fuse in the 12v power outlet so have taken off the front to change it. ... Hello zenith9, you're right, that is the fuse holder, I think it is a 'push together and turn anti ... '11 Kymco Downtown 300i ABS - 79,500km
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bad fuse ? if u have light try to take out of gear maybe start in gear function bad or try to short starter relay

Check the kill switch on the handle bars I have had them short out and also check the wire from the kill switch to the plug in on the bike. if that is good it maybe the Ing switch has a short. Hope this helps

check cableling and fuses

my top speed is 150 kmh. ( 94 mph. ) I seen one from Germany his top speed was 182 kmh. don't know what he did to do that,. at 8,000 rpm that's on the speedometer, not true speed ,.I have had mine up to 8,000 rpm and only 150 kmh. he must be going down hill,. I did it only for 1/2 mile don't want to loose my lic.

the fuse is under the front plastic cover take it off and install a dash mount fuse in the glove box, beside the outlet plug it has # 20 wire in there, ask electrition how big a fuse you can put in there, or install wire from the battery with # 12 wire, and close the small wire off,