Can someone tell me hot to acheive that kind of effect?

Try my plugin metallic with the color blue on certain blend modes. It might be able to do something like that. but remember, The gimp layer and its content switches blend modes, not metallic.

Thread about Metallic
viewtopic.php?f=9&t=19927&start=10

Metallic Plugin Download
https://github.com/LinuxBeaver/gegl-met ... L/releases

This low-res image may have been done with AI. If it was it's being fed-back to humans to analyze. The luminous parts look like circuitry and the holographic bit is on a higher layer. The hand is attempting to hold this piece. So keep the blue luminous goo off the hands (fuzzy select).

I would use AI first with prompts like 'circuitry, holographic, floating, luminous'.

This image is from the Marvel's movie Spiderman: Far from home > https://youtu.be/BA2LrQ7zPA0?si=h1KsVYzhBRUrNBYE&t=73 ( the timing I put on the video link should be at a second from that moment )

If you want a similar background I'm not sure but with the image, you could grow your selection one pixel add another transparent layer then turn the selection into a path. Selection to none, Stroke your path using a brush - maybe a dash brush? or one to your liking. Set your brush dynamics to 'track direction' and stroke with 'paint brush and emulate brush dynamics.' For your spacing you may need to do it and undo a few times to get it right. after you have got that how you like then turn your opacity down on that layer if you do not want at 100%

Very first time I tried to do this, so bear with me....