What are the most reactive metals according to the metal activity series?

The most reactive metals in the activity series are the elements in Group 1 — the alkali metals.
A ranks metals in the order of their ability to displace the ions of elements below them in the list.
Any element can displace any other element that is below it in the list.
But truthfully, one of the most reactive metal that’s always left out in the reactivity series is francium, ##”Fr”##.
The half-life of francium is so short (20 min), there is so little available, and it is so reactive, that chemists haven’t been able to make the measurement.
Current estimates are that ##”Cs”## and ##”Fr”## may be tied in the activity series.
The reactivity depends mostly on how strongly the metal wants to hold on to its electrons (its electronegativity).
The lower the electronegativity, the more reactive the metal will be.
In the Periodic Table, electronegativity tends to increase from bottom to top and from left to right.
So the most active metals tend to be at the lower left of the Periodic Table.