Can metal melt

Answer 1

Yes, all metals, both pure (element) and alloys, can be melted; though some require large heat inputs at very high temperatures. By contrast the lowest melting point is of a lead-tin-antimony-bismuth mixture called "Wood's Alloy", at about 70ºC.

Answer 2

Yes metals do melt at a sufficiently high temperature, but they have high melting points so a very large amount of energy is required to change them to the liquid state. Group I elements like sodium have lower melting points though, so it becomes relatively easier to cause them to melt through strong heating.
Yes. Mercury is liquid at room temperature. The Earth's core is made of molten iron and other metals. Metals melt at different temperatures, depending on which metal it is and whether it is a mixture or alloy. Several parts in your car's engine are castings, which is a process of pouring molten metal into a mold and waiting for it to cool. The block is cast, and other parts too, depending on the manufacturer. Most gold jewelry is also cast as part of their process. Here is a table with some of the temperatures:

http://www.engineeringtoolbox.com/melting-boiling-temperatures-d_390.html