High-frequency trading generally has a large affect on the volume of trades occurring. The more orders in the market, the more people who can buy. Large volumes of trades entering the market also mean that the prices are updated regularly, meaning valuations are more accurate. Having said that, both of the above are a bad thing when something goes wrong. If a bad price enters the market, the volume of trades done on that bad price are huge. This can have a very large affect on the market.
High-frequency trading (HFT) significantly influences market liquidity and volatility. While HFT can enhance liquidity by narrowing bid-ask spreads and facilitating quicker transactions, it may also contribute to increased volatility due to rapid price fluctuations driven by algorithmic trading strategies. The dual nature of HFT means it can both stabilise and destabilise markets, depending on prevailing conditions.