Steel: Cast-iron: As said earlier steel is usually flat sheets welded together and cast-iron is ornate sheets bolted together. Pure stainless is non-magnetic. Most stainless appliances today are made from a thin stainless skin pressed onto a normal steel base, sorta like oak veneer on flake board cabinets. KaptJaq
Which begs the question: what stainless alloy? There are many stainless alloys, with a variety of properties. Typically 300-series are not magnetically susceptible, but 400-series are, ferinstance. So, "stainless" likely isn't "stainless" unless you specify WHICH stainless.
The magnetic properties are most affected by the levels of chromium and nickel as well as the amount of cold working. In most cases the magnetic properties of most stainless steels the common homeowner comes in contact with are non-existent or radically less than normal steel or iron. Specialty stainless steel is a whole 'nother topic. Most home appliances we have worked with have a stainless clad carbon steel skin with a good level of stain resistance, higher levels of nickle... but the carbon steel layer makes it appear to be magnetic stainless. KaptJaq