So to begin the guide part
Mordekaiser is a Amazing tanky jungler and top laner
He is truly the personification of a Juggernout
You as a champion provide alot of Tankiness to the team and alot of Suprisingly high damage especially vs tanks as your passive does a Max Hp DOT damage
you have consistent damage and tankiness also making you one of the best 1v1 champions to exist
Here are some good tips to learn this beast
Your Passive Is one of your main damage sources appart from your Q
Your Q is your primary source of damage and your bread and butter
Your W is your secondary outplay tool and a great burst of Sheilding and Healing
Your E is your main outplay and ingage tool and is usually how you start every fight
Your R is one of the best ults in game especially to solo out the enemy carries and key enemies to win a fight
Some simple mechanics for Mordekaiser
You can throw your e backwards to pull enemies away from you when running
Your R arena is based off of the enemies position x your position so when ulting make sure you give them as little space as possiable
this mechanic can be heavily abused as your ultimate gives the enemy more space to move and run away which you can with some practice make less space for them and also close the gap between you and the enemy

You start your Jungle
on the red buff
you Always full clear and go in this order
Red
krugs
raptors
wolves
Blue+gromp duo camp
Scuttle
people underestimate how good the mordekaiser clear is youre able to sometimes on a good clear even invade the enemy depending on the enemy champion
You have amazing invade and 1v1 potential and should try to always get deep vision and steal the jungle
as for ganks unlike top lane you save your e for flashes and most focus on the enemies movement to actually hit them after than if your laner responds correctly you should easily kill the enemy laner
make sure to focus objectives as well
as your passive % damage applies onto them very well dealing up to 100 damage per second