Could somebody give me an example of a grounded metal object and how touching one can prevent you from getting shocked or electricuted.

 

consider your oven/geyser/water heater/electric iron etc...
these devices primarily require a ground (earthing)connection because chances of leakin charges is high..this is due to the high het produced by these devices is sufficent to melt the insulation on prolonged use.. more over most of these devices darw a large amount of current (so that they can heat generate heat) and hence chances of leaking charges is higher..
these leaked charges accumalate on any mettalic surface and act as staic charges..they spread out with uniform density(charge density) on the surface of the metal(Gauss' Law)..as a result of this a electric potential of the metal builds up which is directly proportional to the charge density..
on contact with a conductor..like human body(which is not sooo much of a gud conductor but nervertheless still conducts)..the charges flow thru the body to the ground..now the ground is like an infinite sink/source of charges... so its potential is always zero...now if this metal were "short circuited" -offered a path of even lower resistance ... lieka maetallic wire to the ground..the charges prefer that path over the body'a path..
hence this prevents the body in contact from gettein shocked..
afuse is ussually connected which burns out in cases of short circuits that disconnects the circuit from the mains supply

 

Just be aware that you can still be shocked when touching a grounded metal object. Your body will provide a parallel circuit to the current. The majority of the current will flow through the "grounded" object to ground but your body would also provide a path for that current.

 

That's where it pays to have a grounded wrist strap when working with static sensitive devices. The built in resistor limits the current and it bleeds the voltage off safely to ground.

If your working with any thing over say 24 volts it's best to use rubber gloves if you don't want a leathal shock if you touched a ground accidentally while touching higher voltages.