Why is high volume important?

High volume is a clear sign that many buyers and sellers are interested in the given asset (may it be a stock, currency pair, commodity, …).
A high volume near resistance levels is a sign many traders are willing to defend this line. The same is true for a support level.

When price is moving in a trend, might it be an up or down trend, an increase in volume when price reaches new extremes is a great signal that this trend is likely to continue.

Heavy volume is a sign of strong interest from many traders in the asset at current price levels.

Why is low volume important?

Low volume is a sign of low interest from the traders. It might be because traders are not interested in the asset or it might indicate price reached low interest zones. These zones can be either too high (no new buyer is willing to step in) or too low (no new seller is willing to step in).

When prices reach new highs but volume decreases, it might be a sign that buyer interest is slowing down and the up trend could reverse. The same is true for a new low but reversed (the down trend could reverse).

There are many volume indicators

All these hidden interest indications are visible when you encompass a volume analysis in your trading strategy.
Here, you’ll find more than 10 volume indicators described here. Each of them can greatly integrate with chart patterns so you can increase your chance of a trade going your way.