You use a standard HSS bit for mild steel.
Stainless steel
Drill bits are made of steel, and often coated with titanium or cobalt.
Cobalt drill bits are good
Coated carbide is the best. Uncoated is next.
Cobalt Drill Bits Ideal for drilling into hardened steel.
High Speed Steel aka HSS
Drill bits can be made from steel which is a mxture compriing mainly of iron. Many drill bits are coated with a very hard yellowish chemical compound titanium carbide. (made of titanium and carbon)
I have worked with tools over 40 years and never seen an iron drill bit. Most common drill bits are HSS -High Speed Steel.
The drill bits used to drill steel come in different colors. The packaging will indicate what materials can be drilled.
Drill bits are made from steel. Specialized bits have enhancements to the steel to increase hardness or maintain sharpness. Magnesium, tungsten, titanium, chromium, vanadium, and molybdenum are elements added to steel for special purpose uses. A few types of extremely specialized bits don't use steel. For example, a bit designed to drill through glass will have a cutting edge of an abrasive such as diamond chips.
Drill bits can be made from steel which is a mxture compriing mainly of iron. Many drill bits are coated with a very hard yellowish chemical compound titanium carbide. (made of titanium and carbon)
Hss drill bits, Titanium coated drill bits and brad point drill bits.
Carbide drill bits are one of the best drill bits available. They don't appear to have major problems. They seem to drill better and have better power than some other types.