Can metals be melted in hot water or just by the heat of a human hand?
Some can and in this video I melt a bunch of them!

Here's where I bought the samples if you are interested in trying this yourself:
(it's much better in real life than on video ;)

www.crystalgrowing-shop.com (German site, most is available on eBay too)
- Rose's metal
- Wood's metal
- Bi-Pb-In-Sn-Cd (in rare cases called French's metal)

www.smart-elements.com
- cesium
- gallium in vacuum ampoule

www.eBay.com
- gallium
- Field's metal

The mercury is from antique mercury thermometers.

Link to the Hg-Tl pictures I use with written permission:
http://www.periodictable.ru/081Tl/Tl_en.html
If you are interested in elements you should check out the rest of his website. His thorium sample is the best I have ever seen!

There are only few sources about the very specialized Na-K-Cs alloy. I have since the making of this video found another source that mentions these compositions and melting points:
12% Na, 47% K, 41% Cs = Melting point -78 C
3% Na, 24% Na, 73% Cs = Melting point -76 C
So no doubt that Na-K-Cs is the metallic alloy with the lowest melting point at around -78 C, but the exact composition is a bit of a mystery...

Royalty music from Kevin MacLeod, www.incompetech.com
Tracks used:
ISRC: USUAN1100694 - Devastation and Revenge (3:19-4:03)
ISRC: USUAN1100850 - Constance (4:03-4:41)
ISRC: USUAN1100403 - Faceoff (8:25-8:46)

Subtitles coming soon in English and Danish.