It's my dad's drill and it's a Bosch. I'm not sure about the model no. etc because the box is missing together with the manual. He's been using it to drill holes in wood to install doors and also walls to hang pictures. I'm not sure if it can drill through steel though provided that if I'm using a drill bit suitable for that purpose (I'm not sure if there's drill bit to drill steel also). The steel that I want to drill is not stainless steel. It's just a 2cm x 6cm rectangle hollow bar and the thickness of the steel is somewhat close to the thickness of a normal kitchen knife (the chef knife as people usually said. not those machete / butcher knife thickness). It's quite rusty too. So can it be done?
Most drill bits sold are "high speed" drill bits intended for a variety of materials including metal (but not concrete, tile, glass or extended use in plaster or plasterboard).
If the bits are fairly sharp, you should be able to use them in the steel, assuming it is not a hardened alloy. To improve your chances, a bit of oil or cutting fluid at the cutting point will help prevent overheating. Slower is usually better.
The rust probably makes the steel weaker and easier to drill.
Drilling steel is easy, once it is marked and punched. I would use a 4 or 5mm high speed steel bit. It needs to be sharp, and sharpening it is a trick: you would need to be shown, as I can't easily describe the technique in words.
Drill on faster speed pushing fairly hard, with some sort of oil (CT-90), by piloting you remove the very centre, which in effect you are not drilling, you are just forcing the bit to push the steel to the cutting edge.
From there you can open the hole to the desired size. For any size from about 9mm I would use the slower setting, and personally I would only drill up to a 14mm with a pistol drill. Keep a tight grip! For anything bigger use a pillar drill and keep the work clamps; the drilling speeds vary depending on size and material, you can look this up.
If you do come across stainless then half all drilling speeds, and keep the cutting constant as stainless will work harden. Brass needs to treated the same, aluminium and coppers are softer and you can nearly double the steel speeds, use appropriate cutting compound for the type of metal.
When drilling metal the bit does not need lubrication! What it needs is cooling for the excessive heat, instead of oil use cutting fluid to cool and save your oil for lubrication B)
If it's too small a job to warrant buying cutting fluid, use water in a spray bottle to cool down your bit. Cutting fluid is a water-oil emulsion itself.
Also, make sure you're starting with a pilot hole before swinging straight for the fences. Even with a drill press, it's wise to always start with a pilot hole and expand it from there.
If you are using a drill bit suitable for steel, then yes, providing the drill itself has enough power, this will be fine.
Even a low power drill can do this successfully, you will just need to take it slow in order to avoid getting the bit stuck. A higher power drill will manage without much of a problem.
As long as it is not hardened and tempered like a knife (which is somewhere between "the drill bit is not that much harder" to "it's harder than the drill") - yes. But even in that case, you would just need a different drill bit, not a different drill.
Something obvious to most here should still be said given that the question implies the asker may be really inexperienced with an electric drill:
Many electric drill can be set to impact (eg for drilling concrete) and non-impact mode (eg for drilling wood). Be sure to choose non impact mode for steel.