This will have a much cleaner explanation if we bring up the the actual formula used to calculate damage in Pokemon (credit Bulbapedia), here:
If you do not know what any of the terms in the equation are referring to, check the Bulbapedia article linked above; most of these should be fairly self-explanatory. With regards to your exact scenario with Scizor, Fury Cutter's boosted or unboosted base power would be considered in Base and its STAB from the move in STAB. Mechanically, Technician directly boosts the base power of a move according to Bulbapedia and so would not be considered in other as it usually would be along with held items, other abilities, weather effects, etc.
Again, according to Bulbapedia, Metronome is also an exception to the normal scenario in that it also boosts the base power of a move instead of being applied to other like held items normally would. So, depending on the scenario, it would play out like this (not considering STAB which is calculated separately as seen above):
First Fury Cutter: 40 base power × 1.5 from Technician × 1.2 from Metronome = 72 base power
Second Fury Cutter: 80 base power × 1 from Technician × 1.4 from Metronome = 114 base power
Third Fury Cutter: 160 base power × 1 from Technician × 1.6 from Metronome = 256 base power
Fourth Fury Cutter: 160 base power × 1 from Technician × 1.8 from Metronome = 288 base power
Fifth+ Fury Cutter: 160 base power × 1 from Technician × 2 from Metronome = 320 base power
So unless Bulbapedia's presentation of the mechanics are wrong, that's how this scenario would work. I cross-checked with Pokemon Showdown's damage calculator, and it seems that it makes no difference to the damage if I put a boosting item on Scizor or if I take it off and manually increase its move's base power. So unless two sources are wrong, this is how the move interacts with Metronome.
Also, I felt like I should mention: 40 x 1.5 is 60 and so Fury Cutter wouldn't get very close to X-Scissor on its first use. Metronome helps with that though, and by the second use it's already far stronger. Though the net gain of using Technician + Metronome + Fury Cutter only surpasses that of X-Scissor + Life Orb after the third use, so personally I wouldn't advise using this strategy over X-Scissor + Life Orb. Most competitive Scizor sets just use U-Turn anyways!
I hope this answers your question! If anyone wants to correct any of my working/ the mechanics feel free.