Why do the following things not cause electric shock? Touching a cooktop heating element, or touching a soldering iron tip or metallic holder, touching the top of the electric grill... how is the transfer of heat accomplished efficiently without transferring electricity ? In the electric grill, the heating element seems to be in full contact with the metal cooking surface?

 

Have a care. Touching certain types of heating element in the wrong place can be very dangerous as they are live electrically.

There are two types of heating element.

Those that are just a length of resistance wire (maybe coiled) strung between the line and neutral of the mains. If you touch the wire towards the neutral end you will not receive a shock, but you certainly will if you touch the wire towards the live end.

Heaters in this category include toasters, hair dryers, convector and fan heaters and some types of electric grill.

The second type of element actually has a fairly complicated internal structure inside the metal outer sheath you see. The metal outer sheath is actually earthed for safety so you can't get a shock. Inside there is the actual heating element, embedded in an electrically insulating matrix that can withstand the temperatures reached and pass the heat to the outer sheath. These can be recognised by being of much larger cross section (ie fatter) than plain wires.
Typical uses are cooker rings, cooker grills, kettle elements, wash boiler elements, washing machine elements....

This is apart from the obvious danger of being burnt.