Is it possible to make distinction between the touch of a bare hand and an aluminum can?
Generate an alternating magnetic field. The presense of aluminium will do two things. First it will reduce the inductance of the coil that generates the magnetic field and, secondly it will remove energy from the magnetic field.

If the alternating magnetic field is produced by an oscillator whose frequency is determined by the coil inductance i.e. a simple LC tank oscillator, then the frequency will rise as conducting metal approaches. This is also called eddy current induction.

If the oscillator is designed appropriately and carefully, the amplitude will also drop indictaing that energy is being removed due to resistive losses in the can (due to the induced eddy currents).

So there are two effects when a piece of metal gets close; frequency rises (normally) and amplitude drops (always). It's called a metal detector if you want a name for it and, most cheap beachcombing devices will indicate the presence of metal due to subtle frequency changes. More sophisticated devices will resolve both resistive and inductive changes and you will find that a lot of metals have different ratios between resistive and reactive components of the signal. This can be used to differentiate one metal from another.

Ferrous metals can reduce oscillator frequency due to the iron channeling magnetic flux and this appears like the coil's inductance is increasing hence the frequency drops. Some stainless steels can both channel flux and receive induced eddy currents and the net effect on frequency can be no change at all BUT there will still be energy lost into the material from the oscillator and this can still be detected and will be a much bigger signal than the resistive losses due to your hand getting closer.

If your hand came close to the active surface of a metal detector there would be a resistive loss and virtually no change in operating frequency. You can use this idea to detect a can whilst ignoring the presense of the hand.