Select one or more objects with multiple materials and another object with just one material as the active object, that will be the Active Object.
In the material list open the v menu and choose ‘Copy Material to Others’
This will copy the material settings to all selected objects.
* Link materials command will not achieve the result, it will still keep unneeded materials on selected objects
Enable the built in addon: ‘Material Utils Specials’
This addon will add three extra material operations to the material V menu:
Clean Material Slots:
Deletes unused material from the object
Remove Active Slot:
Same as deleting a material by pressing –
Remove all Slots:
Delete all materials assigned to the object