Best distortion/OD pedals for classic heavy metal?

What are the best distortion/overdrive pedals for getting a classic 80s heavy metal tone (ex. Iron Maiden, Megadeth, Metallica, Judas Priest, etc)? I know a lot of those bands have wildly different tones but if anyone could name some pedals that can help push your tone towards the likes of that it would be greatly appreciated!

Also, does anyone know if bands such as those listed above actually used pedals or did their sound derive directly from overdriven amps?