The S&P/ASX 200 Index (ASX: XJO) is having a tough time on Friday the 13th. At the time of writing, the benchmark index is down 0.6% to 8,283 points.

Four ASX shares that are falling more than most today are listed below. Here's why they are dropping:

Metcash Ltd (ASX: MTS)

The Metcash share price is down 4% to $3.23. This is due to the wholesale distributor's shares going ex-dividend this morning. Earlier this month, the wholesale distributor released its half year results and posted a 5.5% decline in underlying profit to $134.6 million. This led to the company's board cutting its fully franked interim to 8.5 cents per share. Eligible shareholders can look forward to receiving this dividend on 29 January.

Regis Resources Ltd (ASX: RRL)

The Regis Resources share price is down 5% to $2.72. This follows a sizeable pullback in the gold price overnight. It isn't just Regis Resources that is falling on Friday. At the time of writing, the S&P/ASX All Ordinaries Gold index is down 2.5%. Bell Potter is likely to see this as a buying opportunity. It recently put a buy rating and $3.35 price target on the gold miner's shares. This implies potential upside of over 20% from current levels.

Rio Tinto Ltd (ASX: RIO)

The Rio Tinto share price is down 2% to $121.70. This follows a poor night for the mining giant's shares on Wall Street. This appears to have offset some big news in relation to the miner's lithium ambitions. Rio Tinto advised that it has approved a US$2.5 billion (A$3.9 billion) investment to expand the Rincon project in Argentina. Management believes that this demonstrates its commitment to building a world-class battery materials portfolio. Rincon's capacity of 60,000 tonnes of battery grade lithium carbonate per year is comprised of the 3,000-tonne starter plant and 57,000-tonne expansion plant.

Vulcan Energy Resources Ltd (ASX: VUL)

The Vulcan Energy share price is down 11% to $5.91. This has been driven by the lithium developer completing a capital raising. According to the release, a fully underwritten institutional placement and strategic placement raised 100 million euros (A$164 million). These funds were raised at A$5.85 per new share. This represents an 11.9% discount to its last close price. Vulcan's managing director and CEO, Cris Moreno, said: "The Placement positions us to continue to commence execution for Phase One Lionheart Project, in line with Vulcan's strategy to implement the world's first carbon neutral integrated lithium and renewable energy project."