Hello!
The most highly reactive metal element group is group 1, or alkali metals.
The reason being is that elements biggest goal is to achieve a stable composition, or have a full valence shell in other words. This being said, for this group to be considered stable they only need to lose one of their electrons in ionic bonding to achieve that full shell.
Group 17, Halogens, is considered the most reactive for non metals because it only needs to gain one more electron in its shell in order to achieve noble gas state.
Hope this helps answer your question!