Metallurgix is a famous sickle maker, and the distant cousin of Obelix. He is the spitting image of Obelix, except that he is small.
Like a miniature reproduction of Obelix, his distant cousin Metallurgix (or Amerix, depending on the translation), who is scrawny and small, is the most famous maker of golden sickles in Lutetia. In fact, Getafix won't go gathering mistletoe anymore if not with a sickle signed by Metallurgix!
As a result, Obelix' cousin is worth his weight in gold, which arouses envy all around and gets him captured by racketeer Navishtrix, the thug who organizes heavy trafficking in golden sickles right under the shadow of Surplus Dairiprodus. Fortunately, thanks to Asterix and Obelix, Metallurgix can enjoy freedom again, along with a menhir offered by his cousin.
Remember that it's Metallurgix who gave our heroes the chance to have their first trip outside the village, and that Obelix, who goes along with Asterix throughout the album for the first time, takes an active part in the intrigue. A few albums later, our favorite anti-hero Obelix had racked up so many heroic deeds against the invading Romans that nobody would even think of calling Metallurgix the "big success in the family"!