Sulfuric Acid as an Oxidising Agent

To be safe I will use Sulfuric Acid in the context of the industrial process.

During the production of Sulfuric Acid, the sulfur in sulfur trioxide is oxidised as it forms oleum.

SO3(g) + H2SO4(l) -> H2S2O7(l)

In other cases where it is not an oxidising agent in the industry:

In dilute solutions, hydronium ions acts as oxidants. It attacks any metal which is above the reactivity of hydrogen.
In concentrated solutions the sulfate ions become oxidants and it will only oxidise metals whose reactivity is above lead in the activity series (in some cases it will cease rapidly due an insoluble product which coats the surface of the metal).

Cu(s) + 2H2SO4(l) -> CuSO4(aq) + SO2(g) + 2H2O(l)
The sulfate ion is usually reduced to sulfur dioxide (but hydrogen sulfide or sulfur may be produced in certain cases). Concentrated sulfuric acid also oxidises bromide and iodide ions.