Easiest Metal Riffs / Songs?

Smoke on the water and Breaking the law

For Whom The Bell Tolls is a pretty beginner friendly song.

hi Dominik and Alexander, you should try these songs
A7X - I wont see you tonight part 1 ( the rythm its pretty easy except on the clean parts)
Metallica - Seek and destroy ( its not to crazy and with some hours of practice you will get it)
Metallica - Wherever i may roam (the rythm guitar its not hard)
Megadeth - Symphony of destruction
Pantera - Five minutes alone
Motley Crue - Shout at the devil
i think are easy songs, maybe not the complete song on some cases but hey its something to start can't wait to see you playing these songs and progressing

Some of the riffs I learned early on that were easy enough to pick up in a day or two were
Rammstein - Sonne
Deep Purple - Smoke on the Water
Black Sabbath - Iron Man and if you down tune to Drop D it becomes insanely easy and makes the slide much easier.
Lamb of God - Descending was tricky for an afternoon or two but once you pick it up it's fairly easy and cool sounding!
Megadeth - Symphony of Destruction
Pantera - Walk
Metallica - For Whom the Bell Tolls
Gojira - L'Enfant Sauvage is really down tuned and pretty easy. 80 percent of the song is an open c string repeatedly played.
Iron Maiden - Blood Brothers main clean riff is a bit of a finger twister at first but it sounds so good and it's a Maiden lick!
Judas Priest - Breaking the Law
A faster paced riff compared to the rest in here that with practice Avenged Sevenfold - Critical Acclaim. It's faster than most on here but it's a sick riff that once you pick it up it's really fun to play and really chuggy!

Good luck to you and your brother!