Using ab initio density functional approach, we analyze the trapping behavior of Hydrogen atom in a series fcc structure metals (M = Ni, Cu and Al). From the calculations we found that the potential trapping sites in all these three metals is strongly correlated with the electron charges distribution and the swelling of the nH-Vac cluster is largely determined by the transferring charges of the metal atoms around the vacancy. According to our results, in both intrinsic metals and the metal with monovacancy the hydrogen atoms are always prone to be trapped at the interstitial site with large pre-existed charges and the growth of nH-Vac cluster greatly depends on the charges supplying by the surrounding metal atoms. By our calculations the deficit charges supplying by the nearby metal atoms always accompany a strain energy increment which forbid the nH-Vac swelling. This mechanism is identified in all these three fcc metals. We also found that the formation of hydrogen molecule at the center of the vacancy can only be identified in Aluminum no matter the trapping sites around the vacancy are fully occupied or not. But in Ni and Cu with the same fcc structure H2 molecule are not popular.