I need an amp to start playing the guitar. I would borrow the guitar from a friend of mine to start right now but i need an amp, which price should be around 100€. The music I'd play would be metal and rock, so distortion is important. Sometimes i would play on the clean channel as well though.
Go with either an epiphone valve junior, a blackheart little giant, or similar commercially made 5watt tube amp. Get a distortion pedal that has an EQ on it. And buy used if you are tight on money.

Most new amps in that price range are transitor based solid state modeling amps. They are ok but they are toys and lack the more complex and musical tone of even a cheap tube amp.

Also do not be concerned about the watts. 5 watt tube amps are massively loud and sound full and thick. The wattage is deceptive when i first started playing i thought i needed high wattage.
peavey vypyr 15 or 30 modelling amp are good for metal and has nice cleans.. I don't think you need a tube amp when you are learning, and this thing has 12 different amp models so you can find a sound you like. also it has built in effects so you don't have to worry about pedals or any of that shit until you decide to upgrade your amp.