Metals stocks strengthened on Wednesday on reports of China's higher than expected trade surplus in April, with both imports and exports exceeding market expectations.The commodity sector was further encouraged by German industrial production rising 1.2% in March when a decline had been anticipated.London risers in the sector were led by FTSE 250 iron ore producer Ferrexpo, up 6.1% and 192p, ahead of FTSE 100 steel and iron giant Evraz, which advanced 4.3% to 173p.The construction and materials sector downed tools on the same day, falling nearly 3.0% as companies such as CRH in the FTSE 100 and Galliford Try in the 250 complained about the effects of the prolonged wintry weather. Dublin-headquartered building materials behemoth CRH was the principal drag on the sector, slipping 4.1% to 1376p, with others such as housebuilding and construction group Galliford Try down just 0.4%.Top performing sectors so far todayIndustrial Metals & Mining 1,909.22 +4.62%Forestry & Paper 9,484.18 +2.56%Aerospace and Defence 4,877.08 +2.01%Technology Hardware & Equipment 1,219.10 +1.71%Industrial Engineering 9,383.42 +1.58%Bottom performing sectors so far todayConstruction & Materials 3,689.95 -3.28%Mobile Telecommunications 4,505.24 -0.64%Food Producers & Processors 7,518.02 -0.56%Banks 5,026.76 -0.53%Chemicals 9,309.80 -0.47%OH