The Australian share market gained ground for the eighth month in a row in May, with the benchmark ASX 200 index increasing by 1.9%. 

Despite some volatility at times, heavy lifting by the index blue-chip names was a key driver of the market, with financials, health care and consumer staples offsetting weakness across IT and utilities.

Here is what the Selfwealth community were buying and selling across the ASX through their Selfwealth trading accounts during May.

Which shares and ETFs were the most held?

Banks were on fire again last month, but more broadly, members of the Selfwealth community have backed blue-chips in their portfolios as the ASX hits a series of record all-time highs.

As Commonwealth Bank (ASX: CBA) and Westpac (ASX: WBC) both notched up records, holdings in these stocks outpaced the underlying gains in the respective shares. With the economy showing signs of going from strength-to-strength in its rebound, and the property market also firing, that may have proved enough to incentivise Selfwealth members to hold these cornerstone names. Adding to the blue-chip theme, holdings in Woolworths (ASX: WOW) grew 7.1% by value, and the stock was the second-biggest net mover in terms of valuation percentage change. Much of the rise pre-dated any lockdown-associated panic-buying, rather, Woolies looks to have gained strength amid market-wide sentiment favouring defensive names.BHP (ASX: BHP) was one of the few stocks to see a decline in the value of holdings across the Selfwealth community, despite a flat performance and major movements in iron ore prices. Instead, Fortescue Metals Group (ASX: FMG) closed the gap on its peer, looming likely to overtake it for the first time.As We'll touch on below, buy-now pay-later names also eased down the list as they saw a dramatic drop in value, however, trading activity was still lop-sided towards buying activity. Furthermore, the drop in holdings more or less moved in line with share price performances, suggesting there hasn't been much panic in relation to the drop.ASX StockCompany1CSLCSL Limited2CBACommonwealth Bank3WBCWestpac4NABNational Australia Bank5ANZAustralia and New Zealand Banking Group6AFIAustralian Foundation Inv7MQGMacquarie Group8BHPBHP9FMGFortescue Metals Group10Z1PZip Co11APTAfterpay12SWFSelfwealth13TLSTelstra14WESWesfarmers15WPLWoodside Petroleum16FLTFlight Centre17WOWWoolworths18ARGArgo Investments19QANQantas20MLTMilton CorpFor the second month in a row, there were no changes to the leading ETFs held across the Selfwealth community. Vanguard's suite of ETFs remain a favourite among Selfwealth members, and across the board, there was once again an increase in the collective value of each ETF by a mid-to-high single digit percentage. There was one exception, with a 5.7% fall in the value of holdings in BetaShares Asia Technology Tigers ETF (ASX: ASIA) outpacing the underlying drop in the ETF, which shed 3.2%. Some investors may have cut their losses here, with year-to-date gains in the tech-oriented ETF subdued on the back of weak performances from constituents such as Alibaba (NYSE: BABA).ASX ETFsCompany1VASVanguard Australian Shares Index ETF2VDHGVanguard Diversified High Growth Index ETF3VGSVanguard MSCI Index International Shares ETF4VTSVanguard U.S. Total Market Shares Index ETF5A200BetaShares Australia 200 ETF6IVVIshares S&P 500 ETF7NDQBetashares Nasdaq 100 ETF8VEUVanguard All-World ex-U.S. Shares Index ETF9ASIABetaShares Asia Technology Tigers ETF10VHYVanguard Australian Shares High Yield ETF

ASX share trading activity

As the hottest' ASX stock traded by value across the Selfwealth community last month, shares in Fortescue Metals Group (ASX: FMG) traded more than three times the next-highest stock (Zip). With nearly 2,000 trades involving FMG shares, it was also the fourth most-active stock by trade numbers. 

The catalyst here can clearly be attributed to the surge and subsequent pull-back in iron ore prices, which during May hit a peak of around US$230 per tonne, and then dipped back to as low as US$170 per tonne. 

Meanwhile, as alluded to earlier, the selling pressure and decline in holdings in BHP (ASX: BHP) can be seen through Selfwealth members' trading figures, where the buy-to-sell ratio was a lowly 44%, among the lowest of any individual stock in the top 50.Buy-now pay-later stocks, particularly Zip Co (ASX: Z1P) and Afterpay (ASX: APT), continue to draw buying support, even amid softer' share prices. When measured by value, a slim majority of trading activity in these shares were buy orders last month. However, when looking at order numbers instead, buy orders for Zip made up 85% of all filled orders across nearly 2,700 trades. This indicates individual buyers have been responsible for small purchases, with sellers offloading larger parcels.In terms of outliers in the top 20, CSL (ASX: CSL) and GEAR (ASX: GEAR) were the highest-conviction trades, with a buy-to-sell ratio of more than 80%. With CSL being a popular blue-chip, and GEAR being a leveraged play to gain exposure to the ASX, it suggests confidence among some in the Selfwealth community that the ASX bull run may have further to continue. At the other end of the scale, buy orders in A2 Milk (ASX: A2M) were just 35.6% of all orders by value, the lowest of the bunch. However, in absolute terms, buy orders outweighed sell orders by a factor of two-to-one, again indicating a preference among buyers for frequent low-value purchases.Other popular trading ideas outside the top 20 by value but with high trade numbers were Appen (ASX: APX) and EML Payments (ASX: EML), each driven by negative news flow. Nonetheless, trade numbers heavily favoured buy orders, in the case of EML at 85.7%, highlighting the fact that Selfwealth members were keen to buy the dip.Top 20 stocks traded by valueCode SecurityBuy-Sell Ratio1FMGFortescue Metals Group53.0%2Z1PZip Co50.6%3VASVanguard Australian Shares Index ETF51.8%4ANZANZ71.1%5WBCWestpac51.5%6BBOZBetashares Australian Equities Strong Bear Hedge Fund50.1%7APTAfterpay55.6%8VDHGVanguard Diversified High Growth Index ETF49.6%9GEARBetaShares Geared Australian Equity (Hedge Fund)80.1%10BHPBHP44.2%11A200BetaShares Australia 200 ETF37.2%12NABNAB65.0%13MQGMacquarie Group51.9%14PLSPilbara Minerals60.9%15FLTFlight Centre46.5%16KGNKogan50.4%17TLSTelstra48.6%18VGSVanguard MSCI Index International Shares ETF43.0%19CSLCSL87.8%20A2MA2 Milk35.6%

That all for this Trade Trends report, stay tuned for the next edition this time next month!