BENGALURU, Oct 22 (Reuters) - Indian shares reversed early gains to end lower for a fourth straight session on Friday, dragged mostly by metal stocks, while investors geared up for earnings reports from oil-to-telecom giant Reliance Industries and other corporates. The blue-chip NSE Nifty 50 index (.NSEI) closed down 0.35% at 18,114.9, while the benchmark S&P BSE Sensex (.BSESN) fell 0.17% to 60,821.62. The two indexes also posted their first weekly loss in three, as equities continued to trade near record-high valuations and worries over the impact of rising commodity inflation on margins persisted. Selling would likely continue near record levels and the indexes would struggle to rise "till institutional buying has returned," said Gaurav Garg, head of research at CapitalVia Global Research. Domestic institutional investors sold a net $511 million worth in Indian capital markets in the last three sessions, according to Refinitiv data, while foreign institutional investors sold about $19.6 million worth of Indian equities in the same time. Metals (.NIFTYMET) were the worst-performing sector on Friday, with aluminium products maker Hindalco Industries (HALC.NS) falling 4.7% to be the biggest loser on the Nifty 50. A drop in benchmark metal prices hurt stocks, while uncertainty surrounding the impact of regulatory intervention in China also weighed on sentiment, said Anita Gandhi, director at Arihant Capital Markets. Tech stocks (.NIFTYIT) fell more than 1% to their lowest in over a week, with Mphasis Ltd (MBFL.NS) shedding over 4%. Consumer goods stocks (.NIFTYFMCG) fell more than 1%, with ITC Ltd (ITC.NS) leading losses in the sector. Banks (.NSEBANK) and real estate stocks (.NIFTYREAL) advanced 0.7% and 2.6%, respectively. The two sectors benefited from an encouraging COVID-19 vaccination program, said Ajit Mishra, vice president of research at Religare Broking. Reporting by Soumyajit Saha in Bengaluru, additional reporting by Gaurav S. Dogra; Editing by Ramakrishnan M.