Why does Sodium Bromide have a melting point that is higher than that of Sodium ?

The melting point of the above elements/compounds is based on their bonding. Sodium Bromide has ionic bonding (a very strong type of bonding), which involves an electrostatic force of attraction between positive Sodium ions and negative Bromide ions . In comparison, Sodium on its own has metallic bonding. This involves an electrostatic force of attraction between the positive Sodium ions and the negative delocalized electrons circulating around the ions. Despite metallic bonding being a strong type of bonding, ionic bonding is stronger in this case.
This means that more energy (and higher temperatures) are needed to melt the sodium bromide in comparison to sodium on its own, hence Sodium Bromide has a higher melting point.