Garden furniture lives a hard life — UV, rain, frost, and people plonking themselves down on it — so prep matters more than the paint you finally brush on.
Start with the surface. For old wooden furniture, scrape off anything loose, then sand the whole thing back to give it a key. If it's been oiled before (teak, iroko, that sort of thing), the oil has to come off or nothing will stick — degrease it with sugar soap and let it dry properly. For metal, knock back any rust with a wire brush.
Then prime. Bare or weathered wood needs a stabilising primer — Zinsser Cover Stain is a cracking all-rounder for exterior timber and blocks tannin bleed from oak. For metal, Hammerite goes straight onto rust and self-primes, or use Zinsser on galvanised. Don't skip this step, mate — outdoor paint failures are nearly always a primer problem, not a topcoat one.
For the topcoat, you want something built for outside. Little Greene Intelligent Exterior Eggshell is my go-to — it's water-based, flexible, and holds colour beautifully through the seasons. Their Pleat or a soft heritage green works lovely on a bench. Crown also do a solid exterior eggshell if you're watching the budget. Two thin coats always beats one thick one — thick coats skin over and crack.
Colour-wise, darker shades cope better with weathering and hide the inevitable scuffs. A deep green sits beautifully against planting — something like Farrow & Ball's Studio Green or Card Room Green looks the part on timber. If you want a softer, painterly look, Pigeon is a gorgeous muted blue-grey that suits a country garden.
Practical bit: paint on a dry, mild day — not in full midday sun, which flashes the paint off too fast, and not when rain's forecast within 24 hours. Let each coat cure properly before stacking or sitting on it. Re-oil teak instead of painting if you'd rather keep the natural grain — paint and teak oil are a one-way decision.