BGR, the site, which amongst other things, claimed that the Samsung Galaxy S3 will have a full HD 4.3-inch display, has stated that the phone will have a ceramic and metal case (possibly a brushed blue metal) as well as a physical home button where such a button is usually located (below the screen, in the middle).
Jonathan S. Geller quotes a trusted source for the latter statement - adding that the phone won't use the onscreen navigation button introduced on Android 4.0 ICS - and inferred the first one through the invite that Samsung sent for the first one. Samsung handsets have historically used plastic cases rather than metal ones unlike competitors like HTC.
Metal cases might look good but they do come with a number of inconveniences. They are generally heavier than plastic ones, marginally more expensive to produce and can cause some issues with wireless connectivity (remember the iPhone's Antennagate).
The phone is expected to be released at an event in London on the 3rd of May. The invite which only reads "come and meet the next galaxy" could also indicate that there will be more than one device launched. We expect two new tablets, the Espresso 10 and the Espresso 7 to be presented there as well.
Source : BGR