Good metal drill bits required. All the one I buy never seem to do the job. I don't mind paying the required £ if they last and do the job but it's hard to know which ones to get.
They last longer on a slow speed and well lubricated, when needed sharpen them up again, cobolt drills aren't too bad.
Ground flutes - rather than rolled - but either of those brands will be good. Stay with Black - or you can get a Silver (HSS) with a Coating Tin normally (titanium Nitride)
Drill quality is a major factor so use, at least, HSS (high speed steel) ones. What metal are you drilling? Are you using a hand drill or pillar drill? Are you using the 'correct' speed and lubrication? More to drilling a hole than most peeps think...
Try to reduce the wobble inherent when using a hand drill. Probably slow the speed down and use a lubricant... When drilling Steel or Aluminium, you should get continuous 'scrolls' of swarf coming cleanly from the drill. Get a pillar drill
CR, as has been suggested the speed is dependant on the drill size and type and metal to be drilled, very small drills < 5mm need to be run very fast and much faster than most people think. Most drills used for bike work at less than 8mm should be run > 1000rpm (as fast as a hand drill can run) otherwise they blunt easily and will pick up and snap. Its a bit counter intuitive but is the sort of thing you get taught in the early weeks of an engineering apprenticeship https://www.scribd.com/document/76351499/Drill-Speed-Chart
Depends what material you’re drilling as well, I needed some holes through 3mm stainless steel sheet ....nightmare!!
Clamp it to wood/MDF right next to the hole and drill through the sheet into the wood. Clamp(s) will stop the sheet riding up the drill...
Not that Keith, it’s just that SS is so flipping tough and hard to drill it blunts drills in no time!