Commodities are the raw materials the economy runs on — gold, silver, platinum, crude oil and natural gas, copper, wheat, corn, coffee and more. They live outside the world of company shares and bonds, and for that reason they behave differently from the rest of your portfolio. That different behaviour is exactly why they appear in this site’s coverage of diversification: an asset that rises when stocks fall is worth its place even before you consider its own returns. The purpose of this guide is to explain what commodities actually are, how you can buy them sensibly, and — most importantly — how much of them any reasonable investor should hold. Because the honest truth is that commodities are bought as insurance far more often than they are bought as the driver of a portfolio’s growth.
The commodity family
Commodities split into a few broad families, each with its own price logic. Precious metals — gold, silver, platinum and palladium — are driven by inflation expectations, currency moves and safe-haven demand from investors. Energy — crude oil, natural gas and petrol — responds to the balance of supply and demand, and is uniquely sensitive to geopolitics. Industrial metals — copper, aluminium and lithium — move with manufacturing and construction, and more recently with the demand for electric vehicles. Agriculture — wheat, corn, soybeans, coffee and sugar — follows weather, harvests and global eating habits. Even livestock, cattle and hogs, are tradeable commodities driven by feed costs and demand. None of these behave like the others, which is one reason there is no single “commodity market” — there are many.
Why investors add them at all
The case for commodities rests on three ideas. The first is inflation protection: when inflation erodes the value of cash, the prices of raw materials have historically tended to rise with it, so a holding in commodities can preserve purchasing power that cash and even bonds lose. The second is diversification: commodity prices historically have shown only a loose correlation with share prices and bond prices, which means a small allocation can smooth the overall ride of a portfolio. The third is supply and demand on a grand scale — resources are finite, and a growing global population with rising industrialisation keeps pushing demand. None of these arguments is a promise of steady returns. They are reasons to hold a modest slice, not reasons to build a portfolio around commodities.
Gold: the classic
Gold is the most popular commodity for investors, and for good reason. It is a store of value that has been trusted for thousands of years, a traditional hedge against inflation, and the asset investors reach for in a crisis. Its logic is easy to state: when inflation is rising, interest rates are falling, the dollar is weakening or geopolitical tension is building, gold has historically tended to rise. In a genuine stock-market crash the pattern is more complicated — gold is sometimes sold alongside everything else to raise cash, before rebounding once calm begins to return.
The practical question is how to buy it. The simplest route for most people is a physically backed gold ETF such as GLD, IAU or SGLN, which does the storage and insurance for you inside one low-cost fund. For private savers who want to hold the metal itself, bars and coins avoid fund fees entirely but introduce storage and insurance costs. A third route is gold-mining shares such as Newmont and Barrick, which offer leverage to the gold price plus the possibility of dividends — but remember these are companies, with all the business risk that brings, not for the purist.
Silver: the volatile metal
Silver is frequently described as “gold’s more dramatic cousin,” and the description is fair. Where gold serves almost purely as money and ornament, silver has a genuine dual demand — from investors and from industry, where it is used in solar panels, electronics and medical equipment. Industrial demand gives silver upside that gold lacks, but it also ties the price to the economic cycle, which is why silver has historically been considerably more volatile than gold. The higher swings are half the appeal and half the danger. For exposure, silver ETFs such as SLV (physical) and SIVR (physical) are the straightforward choice, alongside physical coins and bars for those who prefer to hold the metal.
Oil: the global economy in a barrel
Oil prices are set at the intersection of supply and demand — supply managed substantially by OPEC and the growth of US shale production, demand driven by the health of the global economy. Add geopolitical events — wars, sanctions, disruption of shipping lanes — and prices can spike violently in a matter of days. That cyclicality is the defining feature, and it is why oil is the least “investable” commodity for most people: timing matters far more than with gold, and retail investors are chronically bad at it. For broad oil exposure the common tools are oil-focused funds such as USO (which holds futures) or energy-sector funds such as XLE (which hold the shares of oil and gas companies), plus wider energy-sector ETFs. Understand the difference before choosing: futures funds track the crude price, while energy-stock funds track companies whose earnings — and dividends — move with it.
Choosing a commodity ETF
If ETFs are the sensible gateway, the specifics of each fund matter more than the asset class label. Total expense ratios (TERs) cut straight into returns, and the underlying structure — physical metal versus futures contracts — determines how faithfully the fund tracks the commodity itself.
| ETF | Commodity | Type | TER |
|---|---|---|---|
| GLD | Gold | Physical | 0.40% |
| SLV | Silver | Physical | 0.50% |
| USO | Oil | Futures | 0.60% |
| COPX | Copper | Equities | 0.65% |
| WEAT | Wheat | Futures | 0.60% |
| DBA | Agriculture (broad) | Futures | 0.85% |
| PDBC | Multi-commodity | Futures | 0.55% |
These tickers are US-listed examples; the exact funds available on your UK platform will differ, so check what is offered before comparing. The broader point holds anywhere: physically backed funds track cleanly, while futures-based funds carry an extra, invisible cost in the form of rolling contracts.
The risks worth knowing
Commodities can swing 30-50% within a single year, which is far beyond what most investors tolerate from shares. Futures-based ETFs face an additional, quieter enemy called contango: because futures contracts expire, the fund must constantly sell expiring contracts and buy newer, usually more expensive ones, and each roll bleeds value even when the commodity’s price goes nowhere. Commodities pay no income — no dividends, no interest — so they cannot cushion a fall while you wait. Physical metals bring storage and insurance costs. And geopolitics, from sanctions to wars to trade disputes, can turn the whole asset class on a headline. In other words, commodities are not passive wealth-builders; they are a bet you place and periodically rebalance.
How much to hold
The sensible answer for most investors is a modest allocation, sized to your appetite for volatility. A common rule of thumb is to keep commodities in the region of 5-10% of the portfolio, rebalanced once a year. Conservative investors may prefer 3-5%, holding gold only, using it purely as crisis insurance. Moderate investors can run 5-10%, mixing gold with a broad commodity ETF. More aggressive investors might stretch to 10-15%, adding silver and some energy or industrial exposure. Whatever the number, the discipline is the same: gold and broad commodity streaks are the diversifiers, not the core of your plan.
Bottom line
Commodities are a useful diversifier and an imperfect but time-honoured inflation hedge. For most investors gold is the sensible starting point, and broad commodity ETFs add wider diversification at the cost of higher volatility. Keep the allocation modest, rebalance it annually, and do not try to outguess the oil price or the gold price. Buy these assets as insurance for the rest of your portfolio — not as a speculative core — and they will quietly do their job. As ever, this is education rather than financial advice, and an adviser who knows your situation is the right person to set your actual numbers.