You're describing a couple tools, sorry.
For straight lines, I like my angle grinder. Bought it for $9.99 at harbor freight. Be careful, there's one with a blue body and one with an orange body. The blue bodied ones tend to burn out very quickly, like within the first hour of use. Get an orange one, order online if you have to. Use a metal cutoff disc with it, they can be had for ~$2 at home depot, online, HF, etc.
I use a hole saw for holes, go figure. I'm talking big ones, over an inch. I clamp the part to my drill press table and use lots of oil in a spray bottle. It's very loud and very slow going, but it works. Leaves a very rough hole, so go a bit small if anything and use a flapper wheel like this:
of the appropriate size and grit (roughest grit you can find) to file down the burrs and get it to fit properly.
For holes 1/2" and under, any HSS (high speed steel) bit from Home Depot is probably good, I have a set with built in pilot drilling tips, which help guide the drill in before it drills the main hole. This can be done with a hand drill, but as you get up towards 1/2" it gets hairy.
Anything between 1/2" and 1" is hard to find, most home drill presses only except up to 1/2" bits in the chuck, and it can be very dangerous drilling something that big. If your part is not clamped down properly and you're not using the correct speeds and feeds, it can grip it and start spinning it around, very dangerous. If you happen to have the bit though, and a decent press, and your part is clamped down very well, step up to the right drill size, going bigger and bigger, so you're not cutting say 3/4 inches of steel all at once. Step drills work well too, I've used mine a number of times, although obviously these are only good for thinner steel:
This is the easiest way to drill holes above 1/2", as they go up to 7/8", and individual drill bits above 1/2" will be expensive, $5-$15 a pop. But again, only for thinner metals.
Made this with my angle grinder, hole saw, and a few little drill bits for the LEDs, my drill press was invaluable.
