Is iron one of the most reactive metals according to the metal activity series?
No, iron is about in the middle of the activity series of metals.
Below is a partial activity series.
There are ten metals above iron and eight metals below it. This puts iron in the middle of the series.
The video shows an experiment to determine the placement of three different metals (Cu, Zn and Mg) on the activity series.
video from: Noel Pauller