Question

Why do Gallium and Caesium melt whem kept on palm of your hand?

Answer 1

Because they have very low melting points compared to most other metals (except for mercury). The melting point of gallium is 29.77°C (85.59°F), which is low enough that the temperature of your skin may be warm enough to melt it. The melting point of cesium is 28.44°C (83.19°F), also within range of normal skin temperature.