I d suggest that a 50mm overlap from edge of gutter mounted on fascia board is adequate.
Minimum roof overhang into gutter.
A typical metal roof overhang may be 2 to 4 inches or even less.
Here phil explains how much overhang a roof should have at the gutter.
2 assuming that you have at least a 20mm overhang into your gutter grab a pair of pliers or multigrips and bend down the valley of your roof sheets into the gutter.
Over this dimension is problematic like you have.
Minimum roof slope adheres to the minimum roof pitch for your specific profile overhangs of metal roofing should conform with design specifications whilst also overhanging at an even length into guttering.
If you already have your roof sheets installed you need to do one of two things.
Some slight overhang is recommended in conjunction with a drip edge flashing to prevent water from getting under the roofing and onto underlying wood.
Metal is usually installed on rafters or strip sheathing rather than the solid decking used under other materials.
In fact in most places i was unable to get my fingers never mind my hand into the guttering to clear it.
1 replace your roof sheets with new ones or.
Looking right down the line of the guttering the gap between the end of the last roof tile and the outer edge of the guttering varies from around an inch and half to in some cases millimetres.
What s probably happened is the slack roof plumber has ordered sheets too long for the job and cutting them back with snips to the correct size a bit time consuming.
This problem can be overcome by having your sheets hanging a minimum of 50mm into the gutter.
What type of sheet has been used.