The S&P/ASX 200 fell 0.58 per cent to 8,856.5 on Monday, ending two days of gains.
A US tech selloff rattled AI-linked miners, and the Reserve Bank looks set to raise rates on Tuesday.
The ASX 200 tracks Australia's 200 biggest listed companies. Think of it as the market's scorecard.
The Nasdaq fell 2.9 per cent on Friday, its biggest one-day drop since June 5, after Intel and Amazon earnings missed.
Investors treat copper as a stand-in for the AI build-out, so it falls when chip stocks fall.
Materials fell 1.35 per cent. BHP lost 1.4 per cent and Rio Tinto dropped 1.2 per cent.
Gold fell 3.3 per cent on Friday to a one-year low, dragging gold miners down for a third straight day.
Most economists expect a quarter-point hike to 4.85 per cent, the highest since December 2008.
Higher rates make borrowing costlier and safe bonds pay more, so some investors sell shares.
AMP fell 7.5 per cent, but Westpac rose 1 per cent on a $6.8 billion full-year profit.
Industrials rose 0.77 per cent and uranium miners shone after their strongest week in nine months.
All eyes turn to the RBA at 2:30 PM Tuesday. A hike would lift mortgage payments further.
Get the full breakdown, key numbers, and what happens next.
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